I checked against
Voip.Ms and Google is cheaper. However
Voip.ms lists 8/10s of a minute to the UK where Google lists 1 cent per minute.
This does not mean that one is better than the other, only that if you plan upon making any large number of calls or long calls, you check all rates. Also check to see if any charges for calls are rounder up to a specific time. If a call costs 1 cent per minute rounded up to the next minute, then 1 min + 1 sec = 2 minutes. Some providers round to the next 6 seconds so 1 min + 1 sec = 1 min 6 sec. That 54 seconds lost can add up, although at a penny a minute I would not be too concerned.
This is why people who plan upon calling overseas sometimes get multiple providers to save money to individual countries or mobile phones, etc.