We have Xfinity Mobile as our primary carrier. Overall, it has been inexpensive and great! The wifi calling and texting is nice. But, the international data roaming can be ridiculously expensive. We have unlocked phones and simply purchased local SIMs in Vietnam during our trip there this spring. We have an Xfinity voice line and the app worked over our Viettel SIM (and local wifi), which was nice as it was our backup number for friends and family to call us.