Hi this phone when u r are not able to send the text message the first thing you can try is reset on the phone which will resolve the issue. MENU--Settings--Phone--Master reset, Select Master Reset to reset the phone to the default factory settings. the default password is 0000.

Not sure what else to tell you. I was suppose to suggest that you contact Fido to have them check on their end. But since you already did and you still can't send messages, just call them again. Hopefully another representative can do something better on your issue. Good luck!