I understand about phoning from U.K. Have you emailed them?
It is so weird, because I use my new email address, that I've only had a few months, and it works. I don't understand why this should be so for me, and not others.
I log in to my GBP store account with the new email address, from any device (new Android Phone, iPad, laptop, desktop etc.) and all works fine. It still shows my registration of Sonar 6, so it's not a new account.
Odd..
Hope you get it sorted soon.