Registered hoping to get some help

I am not sure where to look for information regarding an old Nokia 1100b. I am quite a novice and I have had this phone for a while now. Anyway, I am inthe Cayman Islands and when traveling to the US roaming works for making and receiving calls to and from Cayman but I CANNOT send nor receive text messages. What is the reason for this and is there a way to correct this. I tried asking Cable & Wireless (my provider) for help but after checking some settings and message center numbers the problem persisted. The last explanation they gave me was that the Nokia 1100b was a dual band and I needed a triple or quad band phone when going to the US. However, the calls do go through when roaming in the US. Any suggestions? THANK YOU SO MUCH.