I bought a used phone from a forumer here that was IMEI blocked. Went to Samsung to get it fixed, they changed the motherboard but IMEI was never changed. The technician says that the IMEI is never changed and stays with the device for life. After changing motherboard, problem still persists so I checked with the seller. He was kind enough to take the phone back and went to check wit the telco. Apparently, Celcom also does IMEI blocking. The phone was out of contract yet they made a blunder and blocked it. So be careful.