Originally Posted by Dubai Stu

Verizon uses both CDMA and LTE and would support quad band HSPA. My recollection was a Sprint unlocked phone was the most versatile. I am going to go on a limb, however, and say that you want at least a 6. WiFi calling really isn't supported before that. In theory the iPhone 5s supports it, but there is a reason why most carriers have avoided it on that phone.