Numerous new Google AdSense publishers are reporting that they are trying to get their phone numbers verified with Google AdSense in the UK, but Google is not calling their phone numbers to complete the verification process.
AdSensePro Ashley writes that this seems to be a problem and Google is aware and is working on it.
Thanks for your reports. Please be assured that we are aware that some publishers are currently unable to complete the phone verification process. We are working to fix this issue.
I guess the only solution for now is to wait.
Forum discussion continues at Google Groups.