Default [Q] Phone Not Allowed MM # 6

Hello,

New poster here and I could not find anything on any other threads so I started a new one.

I bought a second hand phone that had previously been unlocked. It was originally locked to Bell and then unlocked afterwards. I used it on MTS for a while and then gave it to a friend to use on Telus but when he put in his sim card it gave the notification "Phone not allowed MM #6"

I did some reading and it seems like that means that the IMEI is blocked but that can't be the case as I can fully use it on MTS.

Does anyone know how I can fix this problem and use it on Telus?

If you need any more information just ask and I will try to get it to you asap.

Thanks for your help!