Send more than 160 characters using for GSM modem

Hi all,

I make a software for sending SMS using for GSM Modem. It's works fine. But my problem is now that it couldn't send more than 160 character.

The error is given below:
" Text is two long. A maximum of 160 resulting septets is allowed. The current input result in 288 septets(given by me)."

// port connected successfully
SmsSubmitPdu pdu = new SmsSubmitPdu(message, cell, "");
comm.SendMessage(pdu);
"

Please help me to find the solution with C# code. Because I have tried it for last two days. But got no solution.

Thanks in advance.