Can't connect to internet on iPhone 5 without wifi?

I've tried restarting the phone and switching on and off LTE and wifi, but none of it has worked. Texting and calling does not seem to be affected, but I can't access the internet or emails without wifi. This problem has just started within the past few days. Please help!

When you use 3G (if it's still called that), it costs money, based on the download size of the website. You are probably using too much internet and the access has been restricted (by your parents if you are a child). If this is not the case, call the provider.