It is a lot more convenient to use a local SIM card than use the SIM card that you are using in your home country. Here there is something that you need to know. Turkish law requires all mobile phones that operate through a local SIM card to be registered. You will probably have to register your phone and pay 115 TL in tax, or purchase a mobile phone from a shop in Turkey (thus also paying the tax).
If you put a Turkish sim card to your foreign phone probably in 1 or 2 months they will block your phone for usage of Turkish sim cards. You will be excluded from the network as an “unregistered” phone.
When it is excluded, it can be difficult and/or time-consuming to have it reactivated on a Turkish network. How to register your phone:
1. Turn on your mobile phone and press *#06# on the keypad to reveal your handset’s 15-digit IMEI(International Mobile Equipment Identity) number. Copy the number onto a piece of paper.
2. Take your phone, passport, residence permit and IMEI to a Turkish government tax office, a bank, or a PTT (post office) and request a Certificate of Registration. You will have to pay TL115 for the certificate.
3. Take your mobile phone and your passport to shop of a Turkish Network Operator (Avea, Turkcell or Vodafone). Buy a SIM card, and the clerk will register the SIM card’s mobile phone number with your handsets IMEI number, and with your personal information.