My phone won't use cellular data when there is no wifi available

This started with my iPhone 11 and I now have the iPhone 15 Pro and it is still happening. When I had the 11, one day my phone wouldn't allow me to use my cellular data and no apps would work without being on wifi even though they are able to be used over cellular data. I tried everything from resetting my network settings, turn on and off airplane mode, turn on and off cellular data, make sure all the apps are able to be used over cellular data and are clicked on in the cellular data tab, and even switching phones and the issues carried over. I'm not sure what steps I could take next but I am sure that it doesn't include my carrier due to other lines on my account working perfectly fine and mine being the only issue and not even they can figure it out. My iMessage also doesn't load any pictures when they are sent and I can't download them without being on wifi. Any ideas on what it could be and how I could fix it?