Flowroute calculates outbound call charges based on longest matching prefix against our full rate list, which can be found at the Flowroute Outbound Rates page.
For example, a call to +44 20 7493 8000 would match the longest prefix in our rate list of 44207 and be billed correspondingly at $0.00774/min. Comparatively, a call to +44 33 0123 4050 would match the longest prefix in our rate list of 443 and be billed at $0.0169/min.
It is important to note that when Flowroute adds or deletes a prefix, a change in the rate for calls can occur, although technically a specific prefix's rate did not change. In the example above, if Flowroute were to update the rate list with a new prefix of 4433 at a rate of $0.0110/min, it would result in an effective decrease in charges for calls to +44 33 0123 4050.
NOTE: Rates are subject to change, so we recommend that you periodically check the rates page for the international destinations you call.