In Turkey SIMs must be linked to ID. If you change owner of a phone number it goes trough approval from the government which takes a day.

IMEIs must be registered before sold. If you buy mobile phone from abroad you can use it for few months without registering the IMEI. Then the mobile networks do not respond to the mobile phone, even if you change the SIM. Registering a phone requires a passport, that proves you have visited abroad in that last 6 months. If longer, you cannot register. And the IMEI gets tied to the SIM. Plus, it is very expensive, like half minimal salary.