Hahaha , welcome to Turkey We have 3 networks here.Turkcell , Avea and Vodafone.Turkcell is best.If you want to get clear sounds with your phone you should use Turkcell.

Use your own network with active roaming state.

If you're talking about registering your own phone for use in country , you can do this in customhouse or airports.But you need to have Turkish Passport and 100 Lira Don't event try to change your IMEI.And also we have Wireless Phone Tax (1.1 Lira or 0.6$ per month)