Gamma Horizon vs the Alternatives: Carrier Platform, Channel Service
Gamma is one of the UK's best-regarded business voice carriers — and you almost never buy it from Gamma. A balanced look at what Horizon does well, what the channel model means for support and price, and when AMVIA VoIP or Microsoft Teams Phone is the better fit.
Key Facts
Quick answer
Gamma Horizon is a carrier-grade, UK-backed hosted phone system at £12–£18/user/month, sold mainly through channel partners — so your day-to-day experience depends on the partner as much as the platform. AMVIA VoIP runs from £5.95/user/month with Microsoft Teams integration and the same provider handling your connectivity and security; Microsoft Teams Phone suits businesses that already live in Teams. All three are PSTN switch-off ready — the right choice comes down to price, support model and how much of your stack you want under one SLA.
Gamma Horizon vs AMVIA VoIP vs Microsoft Teams Phone
| Feature | Gamma Horizon£12–£18/user/mo | AMVIA VoIPfrom £5.95/user/mo | Microsoft Teams PhoneLicence added to M365 |
|---|---|---|---|
| What it is | Hosted phone system on Gamma's own UK voice network | Managed cloud telephony with Teams integration | PSTN calling added inside Microsoft Teams |
| Typical pricing | £12–£18/user/month | From £5.95/user/month (UK market typically £12–£20) | Per-user licence on top of your M365 plan |
| How you buy it | Via channel partners/resellers — rarely direct | Direct — one provider, one SLA | Via Microsoft licensing or a partner |
| Who supports it day to day | Your chosen partner — quality varies by partner | AMVIA UK support, same team as your connectivity | Your IT provider or Microsoft support |
| Microsoft Teams integration | Available via partner-configured options | Native — it is Teams | |
| PSTN switch-off ready | |||
| Best suited to | SMEs with a strong local partner relationship | Businesses consolidating phones, connectivity and security | Teams-first organisations with simple calling needs |
When Each Option Wins
Choose Gamma Horizon if...
You value a carrier-grade, UK-backed platform and you already have (or can find) a strong channel partner. Horizon's £12–£18/user/month buys a mature managed SME service — but the partner you buy through determines your support experience, so choose the partner as carefully as the platform.
Choose AMVIA VoIP if...
You want the phones, the connectivity they run on, and the security around them under one provider and one SLA — from £5.95/user/month with Microsoft Teams integration. When a call drops, there's no debate about whether it's the phone platform, the circuit or the network: one number owns the fix.
Choose Microsoft Teams Phone if...
Your business already lives in Teams and your calling needs are straightforward. Adding PSTN calling to the app your team uses all day is operationally simple — though call-centre-style features and analogue-device support are where dedicated platforms still win.
Whichever you choose, choose before January 2027...
The PSTN switch-off on 31 January 2027 retires analogue lines and ISDN for good. All three options here are switch-off ready — the risk isn't picking the wrong one, it's leaving the migration until the rush at the deadline.
The platform is half the price question
UK hosted VoIP typically runs £12–£20/user/month, with Gamma Horizon's published range at £12–£18. AMVIA runs from £5.95/user/month. But the per-seat price is only half the bill: number porting, call recording, handsets and — above all — the quality of the connectivity underneath decide what business calling actually costs. A VoIP quote that ignores the circuit it runs on is an estimate, not a price.
See what business VoIP really costsThe AMVIA Recommendation
The AMVIA Recommendation
Judge the service model, not just the platform. Gamma's network is genuinely good — which is why the deciding questions are who supports you, what the seat really costs, and whether your phones, connectivity and security should live with one accountable provider. AMVIA quotes VoIP alongside the circuit it runs on, so the price you compare is the price you'll actually pay — and if a different platform fits your business better, we'll say so.
Get a VoIP quoteGamma occupies an unusual position in UK business telephony: one of the country's most respected voice carriers, whose flagship product — Horizon — you almost never buy from Gamma itself. Understanding that channel model is the key to comparing it fairly against direct providers like AMVIA or licence-based options like Microsoft Teams Phone. For the wider market picture, see our UK business VoIP provider comparison.
What Gamma Horizon actually is
Horizon is a hosted business phone system running on Gamma's own UK voice network — carrier-grade infrastructure with a mature feature set, typically priced at £12–£18 per user per month in the SME market. Gamma sells it channel-first: partners and resellers package Horizon with their own support, SLAs and pricing. The platform is consistent; the experience isn't. Two businesses on identical Horizon deployments can have very different support quality and bills depending on the partner behind them.
The alternatives, honestly stated
AMVIA VoIP runs from £5.95/user/month against a UK market norm of £12–£20, with Microsoft Teams integration — and the structural difference that the same provider manages the connectivity the calls run over and the security around them, under one SLA. Microsoft Teams Phone adds PSTN calling inside Teams via licensing: operationally simple for Teams-first businesses, though dedicated platforms still win on call-centre-style features and analogue-device support (see our Teams vs Zoom Phone comparison for the app-first landscape). RingCentral, 8x8 and Vonage round out the market at international scale — strong platforms, priced above the UK value end.
The channel question
Buying Horizon means choosing a partner, and the partner determines your escalation route, your response times and your renewal pricing. That's not a criticism — a good local partner is genuinely valuable — but it means a Horizon evaluation is really two evaluations. Ask the partner the questions you'd ask any provider: who answers the phone at 5pm on a Friday, what the SLA commits to in writing, and what the seat price includes. The platform's quality can't compensate for a weak partner sitting between you and it.
The deadline that frames every VoIP decision
The PSTN switch-off on 31 January 2027 retires the UK's analogue lines and ISDN circuits. Gamma Horizon, AMVIA VoIP and Teams Phone are all cloud platforms — all switch-off ready. The genuine risk is timing: businesses still on traditional lines that wait for the deadline rush will find installation lead times stretching exactly when they can least afford it. Whichever platform you choose, choose it in 2026.
How to run the comparison properly
- Normalise the seat price — same features (call recording, mobile apps, handsets), same contract length, before comparing numbers. Our VoIP cost guide breaks down what moves the bill.
- Evaluate the support model, not the brochure — for Horizon that means the partner's SLA; for AMVIA it's one UK team across phones, circuit and security.
- Price the connectivity underneath — call quality is decided by the circuit, and a quote that ignores it is incomplete.
- Check Teams integration depth if your business runs on Microsoft 365.
- Confirm number porting is handled for you — it's the step that goes wrong most often in DIY migrations.
Frequently Asked Questions
Gamma Horizon is a hosted business phone system running on Gamma's own UK voice network — a carrier-grade, UK-backed platform aimed at SMEs that want a managed service. It's best for businesses with a strong channel partner relationship, because Gamma sells Horizon almost entirely through partners and resellers: the platform sets the ceiling, but the partner you buy through sets the day-to-day experience.
Typically £12–£18 per user per month in the UK SME market, sitting inside the wider £12–£20 norm for hosted business VoIP. Exact pricing varies by the channel partner you buy through, contract length, and extras like call recording or handsets. For comparison, AMVIA business VoIP starts from £5.95/user/month — when comparing, make sure both quotes include the same features and the connectivity underneath.
Generally no — Gamma is a channel-first carrier, selling Horizon through a network of partners and resellers rather than direct to end businesses. That model has a real consequence: two companies on identical Horizon platforms can have very different support experiences and prices depending on their partner. If you're evaluating Horizon, evaluate the partner's SLA, escalation route and pricing as rigorously as the product.
Neither is universally better. Horizon offers a mature, carrier-grade platform at £12–£18/user/month via a partner; AMVIA runs from £5.95/user/month with Teams integration and — the structural difference — the same provider managing your connectivity and security under one SLA. If you want to keep an existing local partner relationship, Horizon is a solid choice. If you want one accountable provider for the whole stack, that's the AMVIA model.
Yes — all three are cloud voice platforms, which is precisely what the PSTN switch-off migrates businesses onto. The deadline that matters is 31 January 2027, when analogue lines and ISDN circuits stop working. The risk isn't choosing between these platforms; it's businesses still on traditional lines leaving migration until the pre-deadline rush, when installation lead times stretch.
Five things, in order: the true per-seat cost with identical features included; who actually answers support calls and their SLA; the quality of the connectivity the calls will run over; Microsoft Teams integration if your business uses M365; and number porting handled by the provider. Platform brochures look similar — the differences show up in the support model and the circuit underneath, which is why AMVIA quotes both together.
Compare Your VoIP Options Before the Deadline
AMVIA quotes business VoIP from £5.95/user/month alongside the connectivity it runs on — and compares honestly against Gamma, Teams Phone and the rest of the market. PSTN switch-off migration handled end to end.
Related Resources
Best Business VoIP Providers UK
The full UK provider market compared — RingCentral, 8x8, Vonage, BT and AMVIA.
Teams Phone vs Zoom Phone
The two app-first calling platforms compared for UK SMEs.
Business VoIP Costs
What business VoIP really costs in 2026 — from £5.95 against the market's £12–£20.
PSTN Switch-Off Guide
What stops working on 31 January 2027 and how to migrate without disruption.
Business VoIP
The AMVIA business VoIP hub — features, pricing and Teams integration.