Could be a number of reasons @Bb8
Are you on pay as you go (PAYG) or pay monthly (PM)?
If PAYG, do you have an active bundle or credit on your phone?
If PM, are your bills up to date?
For both, it could be there is a problem with your sim card.
See if any of these guides help, and if not please come back with some more information.
Guide: How can I sort out my network issues?
Guide: Is the network down for me or everyone?
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 Do not publish personal details (email, phone number, bank account).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
