I have a Iphone 3gs but can't use 3G?

Its jailbroken and i only use 3g once then the next day it wouldnt work and whenever I send pictures it won't send

Do you have a data plan?

You can complain to the company. You can also try by rebooting or restore factory settings.

Well that's more an issue of the carrier rather than the phone. You'd have to contact their CSR to get help.