iPhone Not working without wifi

Apps that require wifi to work on my phone, don’t work without it. If I’m in an area with the best service but no wifi, my apps won’t work. I have unlimited data so I’m not sure why this is a problem. I have turned my phone on and off, updated it, and I even took the SIM card out and put it back in. I can still call and message people without a problem. I already talked to my carrier provider over the phone and they said they don’t know why my phone is like this. If you know how to fix this issue, please help!! This issue started 2 months ago. I already made a post about this topic but only 1 person helped