Does the Moto G4 use sprint towers? If not , what towers do they use?
the G4 can use either CDMA (Sprint) or GSM(T-Mobile) on Republic (also CDMA Verizon, CDMA US Cellular, or GSM AT&T just with Republic)
all BYOD are GSM at this time
if ordered from Republic then it will be based on Republic Coverage check Coverage Check | Republic Wireless when ordering (this also is on the phone order page) Top Android Smartphones, payment plans optional | Republic Wireless
There are several ways to figure out what towers/coverage your phone is using. The simplest one I like is using this app