Verification failed could not activate cellular data network

Having constant issue with error message "could not activate cellular data network" and iCloud gives error messages "iCloud verification failed and can not connect to icloud. It also constantly prompts for passwords and will not roam. This issue has followed me over 3 devices and Tech Engineers from Sprint and Apple can not solve the issue. Have done ##update#, ##clear#, restored as new device, Ive deleted backups, etc. I don't know which other direction to go.