Anne, Agazina says mobile 2 mobile is expensive with Avea compared with the other more known ones, like Turkcell.
A turkish sim card means you make local calls in Turkey more cheaply using local networks, rather than UK and back calls.
The other point is ..if you don't top your Turkish sim card up inside every 3 months, it closes down and you lose that number and any credit left on it. ie You start again next visit, unless someone keeps your phone card in Turkey to top up. I think they need that phone also.
I believe it all gets linked up during registration. Passport Required.
Tel