Roaming costs for all countries are listed at https://ee.co.uk/help/mobile/roaming/roaming-costs , Turkey is not in the EU so all usage will incur additional costs.
There will be add-ons available for voice calls, texts & mobile data. Remember to enable roaming access to foreign networks, before leaving the UK, by texting ROAMING to 150.
Failure to do so will mean your phone won't have permission to use foreign networks.
