Is everything else working?
Can you make and receive calls, receive texts and use data?
Can you send texts to these numbers
Your own number from
Zero followed by ten 7,s
+44 followed by ten 7,s
Switch your phone off and remove the sim
Wipe the sim contacts with a cloth
Wait 5 minutes
Now try texting those numbers again
Then try texting your contacts
If you still can't send texts try a reset of network settings
(be aware this will erase your saved wifi passwords, it won't erase or affect anything else)
And click reset network settings
The phone will switch off and restart automatically in a few minutes