Please help with GSM900 and Arduino Mega2560

Official Hardware Retired GSM Shield
2

Hello,
I found the solution here:
http://www.elecfreaks.com/wiki/index.php?title=EFcom/GPRS_Shield_Guide

//SoftwareSerial mySerial(RX, TX)
//SoftwareSerial mySerial(50, smiley-cool; //OK
SoftwareSerial mySerial(50, 51); //OK

Henri