One of the key features of GSM systems, besides connecting user's cell phones, is by using roaming and Short Message Service (SMS). Both these services give you a lot of functionality because you can reach and communicate with others at anytime of the day or night no matter where you may be. You can travel from one state to another and will always know you can get in touch with someone by either through the SMS system, or by making a phone call. If you try to reach someone by phone and their line is busy, you can get in touch with them by using SMS.
Setting up your phone for roaming is automatic. That is controlled by your SIM card and the GSM system. So you don't need to worry over that one. As for SMS, you just need to set it up on your cell phone. Because each cell phone is different, you may have to refer to your phone's user manual to do it correctly. The basic premise here is to find the menu for SMS. You may find it under Messages or Mail. Once you find it you just enter the number of the SMS Center for Short Messages Services your service provides. Once you do this, follow the instructions on the screen and you'll soon have your SMS system activated.