I Can't Send Texts On My Iphone 3gs?

I got a second-hand Iphone 3gs for christmas, but i had to get it unlocked so i took it to my local iphone reapir shop, IRepair and he said there was no pernament unlock and the only way he could do it was by jailbreaking it… Him being the expert i let him do what he wanted, I was promised that everything would work including calls, texts, internet, facebook etc, and everything does except… Text messages, when i try to text someone it doesn't send and it says Message Failed. Could someone please help me please.

I do not understand everything about phones, so I may not know. But do you have a network service (i.e.AT&T, Verizon)?
"Jail breaking" is the term used for "opening up" an iOS system, and letting the iOS device do things it may not be able to do without it. The term "jail breaking" is used mostly for UNIX based systems, such as iOS. I would recommend going back to "iRepair" to get help from someone who probably understands it more than I do. Hope this helps!