Straight Talk CDMA Iphone on one of their other networks

Jan 2, 2019
So I'm trying to figure out my wireless situation. I live in a remote area where I don't get service with any carriers, so wifi calling is a must. I just got an iphone 6 for straight talk because A) it was a deal for just $100 brand new, and B) Becuase the sales associate assured me it would work. Alas, Straight talk's phones that use Verizon's network don't support wifi calling. Also, the phone is locked to straight talk until you've paid for a year of their service. So, if I were to get a different Straight Talk sim that uses say t-mobiles network, which does support wifi calling, would it work? I imagine yes, since I know that the phone has all of the same GSM Bands that t-mobile uses, my only hesitancy is that the phone is locked, but I don't know if its just locked to all Straight Talk networks, or if locked specifically to Straight Talk's Verizon network. Let me know if anybody has any ideas!