Can you let us know the following:
-What phone do you have?
-What carrier are you on?
-By internet, do you mean that you are able to use mobile data through your carrier, or that you can use wifi?
-Does your device have a sim card?
-Is your device or sim card activated on the network?
-Is this a new device or a problem that just started on a device you've been using for awhile?
-Have you made any modifications to the phone software (rooting, custom rom, etc.)?