Internet

I can’t go on the internet unless I am on Wi-Fi. I can receive calls and texts but every time I go on the internet or my App Store it says PDP authentication failure. I have already contacted my carrier and it’s not my carrier issue. They said my phone is defective and to contact Apple for a warranty exchange. Yesterday I was on a call for tech support for over 4 hours trying to resolve and today I went in to talk with my carrier and determined it was a phone defect.