Can anyone tell me a number to override new provider (ya.com) and use telefonica for voice calls?

Telefonica won't release my line to ya.com who bill me and have been billing me for months (bb is fine) but I can't make any calls right now. Usually (well in the UK) you can add a prefix to override a 3rd party provider and be billed by bt for the call. Is this the case here and does anyone know the prefix?
And while I'm here is there a 1471 equivalent so you can get the number of the last person who called?

I've spent so much time trying to find these 2 ickle things out - it's driving me nuts. Any help would be so appreciated.