Wifi works but the 4G internet isnt working. Why, and how can I fix it?

I have data on my phone still, so I dont think thats the problem. Weve been paying the bill, so it didnt get shut off. I havent messed with the settings at all, and I try to keep up with the updates. I believe its updated, so whats the problem? Please help ;-;

Have you made sure that Mobile Data switched on, and tried a Power Off and Restart? Also tried reseating the SIM?