On arrival in Turkey you may want to buy a local phone SIM to save on call and data costs. These can be bought easily at the larger airports or in shopping streets during business hours. The major providers seem to be Turkcell, Turk Telecom and Vodafone. You’ll need to show your passport, which they’ll copy, then complete and sign some forms.
Unless you’ve got a Turkish friend with you, they won’t sell you the “locals” SIM deals. Instead you’ll be offered something like the 1-month Tourist Pack which I bought from Vodafone. 100TL for 300 minutes of local calls, 30 minutes of international calls and 10GB of data (September 2017).
I realised later, SMS messages were not included at all. It’s a good idea to ask the shop to install, activate and test the new SIM for you while you’re in the shop. The SMS instructions you’ll subsequently receive from the provider will be in Turkish so you many need help with the activation process.
It’s also a good idea to take the contact details of the salesman in case you need support later. The activation process sometimes requires a couple of hours to complete. Mine took about 1 hour to come to life and then I had to enter a text activation code, which the salesman had already written down for me.
My Turkish friends varied in their recommendations, seeming to prefer the Turkcell and Turk Telecom SIMS for coverage but the Vodafone SIM for reciprocal benefits in Europe. Vodafone just happened to be the first store I found in Antalya and it was mostly fine, except for one “black spot” where I lost signal for a while travelling between Izmir and Sakran.