You'll need to provide a bit more information than that if you want assistance from the Community Forum.
Is "unable to send message" the full verbatim error message?
Did it ever work?
If so then when did the problem start and did anything change on the phone just beforehand?
Do you get that error message for all texts to any numbers or just for some?
Can you receive texts?
Are incoming/outgoing calls and mobile data working ok?
Do you have an active membership plan in order to be able to use outgoing services?
What make and model of phone is it and what messaging app?
Anything useful here?
If you need to contact 48 support about this then see the links in my signature below.
