how to disconnect GPRS from samsung mobile?

I have samsung dual sim mobile with bsnl prepaid connection. I do not have any internet connection to my mobile. I get messages every ten minutes saying that I have used --kbs cost of GPRS session is Rs.0.02. I called bsnl call centre explaining the problem and asked me to send deactivation sms to 53733. One or two days I will not have any message deducting 0.02 p but again I get same messages deducting 0.02 paise x 20-30 times a day. Also a symbol E1 appears often on screen and I do not understand how to get rid of this problem. Can some one help me?