text messaging my cell phone

i was able to text mess my samsung cingular c207 cell phone from my computer thru aol/aim when i first got my phone , now when i text it i get the same message over and over, "sorry cannot deliver message at this time please try again later" and its been about 3 weeks this has been happening. wondering if any one is familare with the samsung and can help me ? maybe i accidently disabled something in phone. i contacted aol live help and was told that the problem lies within the phone service and not aol's service. please can anyone help me ? this is my only comunication to outside of home from home i have no land line. thank you sara