First, make sure you are not in airplane mode. If you are, switch off your phone and then switch it back on again.
Then, check that your line hasn't been blocked following a request (theft, loss, etc.), due to non-payment of a bill, or (for customers of prepaid cards) because you don't have enough credit.
If the problem is not linked to any of the above, try putting your SIM card in another phone to find out if it's your SIM card or your phone that's defective.
If your SIM card is defective, consult the guide
If your mobile is defective, consult the Mobile guide.
If that doesn’t help, call us on 800 777 77
Consult the SMS and MMS guide.