Could be any number of reasons @RB8
Check if there are any software updates for your phone.
Contact the phone manufacturer to see if there is a fault with it.
Try getting a new sim card (best to do this in your local store - otherwise a new one is sent out and your current one is switched off).
Not sure if this guide will help...
Guide: How can I sort out my network issues?
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
