[Q] T-Mobile wifi calling on i747 topic

My family recently switched to T-Mobile and another family member had my S3. I remember a loooong time ago I installed a i747 ROM that was a tmobile variant port and when I first booted with the rom it said something about tmobile wifi calling not working (because I'm on AT&T). If I wanted to get tmobiles wifi calling on my i747 S3 is there a method or rom that offers that? I tried searching for the rom I used before or a thread about this but I couldn't find one :l