Unlocking Sim Free Samsung Galaxy S3

[AC Question]

My Samasung Galaxy S3 was unlocked from O2 in UK in April 2015 and has become locked again.
How do I unlock a Sim Free Samsung Galaxy S3 which has become locked after 8 month being Sim free?

 

[belodion]

Who did the unlocking? Some unlockers don't do it properly.
Or did you get the code from O2?

Posted via the Android Central App

 

[Kambiz Daneshyar]

The unlocking was done by code given by O2

 

[belodion]

Welcome as a new member.

Have you spoken to O2 about it?

 

[Rukbat]

An O2 phone would be GSM. Once it's carrier-unlocked, it can't be locked again. If it's rejecting another carrier's SIM card, something's wring with the phone.

 

[Kambiz Daneshyar]

The phone works with WiFi but not with a Sim card. Strange !!!!

 

[belodion]

The phone works with WiFi but not with a Sim card. Strange !!!!

No, that does make sense. You can use wifi whether or not the phone has a SIM in it.