Sim card not supported

Good Day......

I was given an iphone 5 by my sister-in-law which was previously locked to TESCO in UK. I asked her to call the TESCO to remove the carrier lock and yesterday she was informed that the lock has been removed. However, when I tried to activate the phone, it still gives the error SIM not supported.

I checked the activation lock status and it's already OFF. Tried to restart, restore, and update the phone but I am still getting the same error.

Also tried reinserting the sim and using other sim (not the one from UK), but still no luck.

Appreciate any input just in case I have missed out on something.

Thanks in advance