(help) in u.k. Voice not working

[anneoneamouse]

Traveling in u.k., voice calling is intermittent (1 call in 15 goes through), failed calls have either no sound or weird clicks. Phone is rooted, and has been reset.

Data works ok. 30 day Period passed during first week of trip, phone was all ok inthe u.s.

Any ideas?

Thanks, Aon