Are all phones still using sprint cell towers or T Mobile?
Some use the CDMA partner [Sprint] and some use the GSM partner [T-Mobile]
all BYOD will use GSM partner
some Phones are GSM only [Moto Z, Moto Z play, Samsung Galaxy J3, Huawei Acsend 5W]
other phones may be ship from Republic configured with CDMA partner if Republic program see CDMA as better coverage