Turn Off Automatic Network when International Roaming
You may now pay the same fixed price (typ 80p/min) on all roaming networks but the features you can access will vary ! For example if you use a UK three mobile in Turkey you'll only get Planet3 if you choose Turkcell.
http://www.three.co.uk/personal/help_support_/abroad_/pay_monthly_country_details.omp?cid=31880