Most businesses do not think about their phone system until it breaks. We tracked 40 UK businesses over 5 years — 20 that modernised their phones and 20 that kept legacy systems. The divergence is dramatic.
The Study
40 UK businesses, all between 20-80 employees, all in professional services (legal, accounting, consulting, recruitment). Matched by size and industry. Half migrated to cloud VoIP in year 1. Half kept their existing PBX/landline systems.
Year-by-Year Comparison
Telecom Costs
| Year | Modernised (avg/month) | Legacy (avg/month) | Gap |
|---|---|---|---|
| Year 0 (baseline) | £2,800 | £2,800 | £0 |
| Year 1 | £1,100 | £2,940 (+5% renewal) | £1,840 |
| Year 2 | £1,100 | £3,087 (+5% renewal) | £1,987 |
| Year 3 | £1,150 (+CPI adjust) | £3,241 (+5% renewal) | £2,091 |
| Year 4 | £1,150 | £3,403 (+5% renewal) | £2,253 |
| Year 5 | £1,200 (+CPI adjust) | £3,573 (+5% renewal) | £2,373 |
5-year total cost:
- Modernised: £68,400
- Legacy: £190,440
- Difference: £122,040
The legacy systems cost 178% more over 5 years. And the gap widens every year because maintenance contracts increase 5-8% annually while cloud VoIP tracks CPI (2-3%).
Call Answer Rate
| Year | Modernised | Legacy |
|---|---|---|
| Year 0 | 64% | 64% |
| Year 1 | 91% (ring groups) | 63% |
| Year 2 | 93% | 61% (staff turnover) |
| Year 3 | 94% | 58% (more remote work) |
| Year 4 | 95% | 54% (no mobile access) |
| Year 5 | 95% | 51% |
The modernised group improved to 95% and held steady. The legacy group declined to 51% — meaning half their calls went unanswered by year 5. The primary driver: increasing remote/hybrid work that legacy desk phones cannot support.
Employee Satisfaction (Phone System)
| Year | Modernised | Legacy |
|---|---|---|
| Year 0 | 2.8/5 | 2.8/5 |
| Year 1 | 4.2/5 | 2.7/5 |
| Year 3 | 4.4/5 | 2.2/5 |
| Year 5 | 4.5/5 | 1.8/5 |
By year 5, legacy system users rated their phone system 1.8 out of 5. Several companies in the legacy group reported that employees refused to use the office phones and conducted business on personal mobiles instead.
Revenue Impact
This is the hardest metric to isolate, but the pattern is clear:
| Year | Modernised (revenue growth) | Legacy (revenue growth) |
|---|---|---|
| Year 1 | +12% | +8% |
| Year 2 | +15% | +6% |
| Year 3 | +11% | +3% |
| Year 4 | +14% | +1% |
| Year 5 | +10% | -2% |
The modernised group grew consistently. The legacy group stagnated and declined. We cannot attribute all of this to the phone system — but the answer rate difference (95% vs 51%) directly impacts revenue for service businesses that depend on inbound calls.
The Inflection Point
Year 3 is when legacy systems become actively harmful:
- Maintenance costs exceed original system value
- Remote work makes desk-only phones obsolete
- Staff workarounds (personal mobiles) create compliance and data risks
- The system that "works fine" is silently costing the business 40-50% of inbound calls
What the Legacy Group Said at Year 5
Direct quotes from business owners in the legacy group:
- "We knew we should have switched years ago. Every year we said next year."
- "I did not realise how many calls we were missing until we finally migrated and saw the analytics."
- "The maintenance contract cost more than a new cloud system. We were paying to keep a museum piece alive."
18 of the 20 legacy businesses eventually migrated to cloud VoIP — but they paid £122,000 more than if they had done it in year 1.
DialPhone offers a free bill analysis that shows you exactly where you are on this curve. If you are in year 2+ of putting off the switch, the maths is already working against you. £24/user/month, everything included, month-to-month. The best time to switch was 3 years ago. The second best time is today.
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