gsm-shield - Arduino Mega Issues

Good Morning, I'm using this library :

http://code.google.com/p/gsm-shield-arduino/

with relative shield. From hardware stand-point it's ok. Now I need to understand how to use correct the library. is there a way to check if are present message all the times ?

also I've tried to use Arduino Mega, I've modified the library like instruction without success: I received this issues:

/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'int SIMCOM900::configandwait(char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:62: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'int SIMCOM900::readCellData(int&, int&, long int&, long int&)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:117: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:119: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:121: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:123: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:125: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'boolean SIMCOM900::readSMS(char*, int, char*, int)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:196: error: 'class HWSerial' has no member named 'getString'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:202: error: 'class HWSerial' has no member named 'getString'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'boolean SIMCOM900::readCall(char*, int)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:229: error: 'class HWSerial' has no member named 'getString'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'int SIMCOM900::getCCI(char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:313: error: 'class HWSerial' has no member named 'getString'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'int SIMCOM900::getIMEI(char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:338: error: 'class HWSerial' has no member named 'getString'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'virtual uint8_t SIMCOM900::read()':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:350: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleRead()':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:356: error: 'class HWSerial' has no member named 'available'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:357: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWrite(char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:366: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWrite(const char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:371: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWrite(int)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:376: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWrite(const __FlashStringHelper*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:381: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWriteln(char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:386: error: 'class HWSerial' has no member named 'println'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWriteln(const __FlashStringHelper*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:391: error: 'class HWSerial' has no member named 'println'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWriteln(const char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:396: error: 'class HWSerial' has no member named 'println'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::SimpleWriteln(int)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:401: error: 'class HWSerial' has no member named 'println'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'void SIMCOM900::WhileSimpleRead()':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:407: error: 'class HWSerial' has no member named 'available'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:408: error: 'class HWSerial' has no member named 'read'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'byte GSM::CheckRegistration()':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:469: error: 'class HWSerial' has no member named 'println'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'char GSM::GetPhoneNumber(byte, char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:748: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:749: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:750: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'char GSM::WritePhoneNumber(byte, char*)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:822: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:823: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:824: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:825: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:826: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp: In member function 'char GSM::DelPhoneNumber(byte)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:878: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:879: error: 'class HWSerial' has no member named 'print'
/Applications/Arduino.app/Contents/Resources/Java/libraries/GSMSHIELD/SIM900.cpp:880: error: 'class HWSerial' has no member named 'print'

What Can I do for fix the issues ?

thanks Gnux