Every wholesale provider will show you a rate sheet, and the temptation is to compare the numbers and pick the low one. The rate is the easiest thing to quote and the least reliable thing to compare, because it says nothing about whether the call connects or how it sounds when it does.
What least cost routing is
A provider has several ways to reach any given destination, each at a different price. Least cost routing is the logic that picks one per call: match the dialled number against the rate table, sort the available carriers by price, send it to the cheapest that will take it.
If the call fails, a well-built platform tries the next one down. That fallback behaviour matters more than the top rate.
Why the headline rate misleads
Rate sheets are per destination, and destinations subdivide much further than most comparisons account for. “UK” is not one rate: landline, mobile, and each mobile network can differ, and the mix in your traffic decides your bill.
A sheet with a very low landline rate and unremarkable mobile rates will look excellent and bill badly if seventy per cent of your calls go to mobiles. Compare against your own destination mix, not against the front page.
Ask for a quote against your real trafficGive a provider a breakdown of last month's minutes by destination and ask what that month would have cost. Any provider who cannot or will not do this is telling you something.
The two numbers that matter more than the rate
ASR — answer seize ratio. The proportion of attempted calls that get answered. It is never a hundred per cent, because people are out, but a route sitting well below the norm for a destination is failing calls that should have connected. Every one of those is a redial, and often a lost sale.
ACD — average call duration. How long answered calls last. A route with a normal ASR but a much shorter ACD is usually one where the audio is poor enough that people hang up and try again.
Cheap routes frequently look cheap precisely because they score badly on both. You pay less per minute for calls that do not achieve anything.
Grey routes and CLI
Some very low rates come from routes that get traffic to a destination by an unofficial path. The tell is what happens to your caller ID: on a grey route it often arrives altered, or missing entirely.
That matters commercially — people do not answer withheld numbers, and they cannot ring you back — and it matters practically, because such routes tend to be unstable and can disappear without warning.
What to ask a provider
- Is this route direct, and if not, how many hops does it take?
- What ASR and ACD does it run at for this destination?
- Is CLI passed through unchanged?
- How often does the rate sheet change, and what notice do I get?
- What happens when the first-choice carrier fails — does the call fall through or fail?
- Is there a premium route available when quality matters more than price?
The sensible position
Not every call needs the best route. Bulk notifications can take a cheaper path; a sales line where a missed call is a lost customer should not.
A provider worth using will let you split traffic that way rather than pushing everything down one route and hoping. Ask about it before you sign, not after the first bad week.
We route UK traffic over Tier-1 carriers and publish the quality figures with the rates.
See our voice routes
