Retired and new cell

[reacon]

My Daughter suggested that I get a cell phone so we could stay in touch by texting, well being new to the tecky world, took some work on my part, texting went great. Anyways cutting to the bones. I'm sure this question has been asked many times. Was texting fine and ran into a snag...my phone will not send a text, get message "message not sent" seem to bounces back to my own phone (A Samsung Galaxy 550). I'm sure I must have done something in the settings, in which I will never touch again if I get this matter solved. Went prepaid perhaps shouldn't have taken this route.

Thanks,
Bryan.