Did they ever send OK?
Can you receive texts?
Can you send to any number or does it fail to send to all numbers?
What happens when you try to send a text?
Any error message?
Do you have a text allowance and an active membership?
Has anything changed on your phone recently - software update, settings changes?
Can you make/receive calls?
Does internet/data work OK?
Plase answer all questions above.
Hope this helps.