I have also read this with big interest after struggling with a Mega 2560. I followed the outlined instuctions and changed to serial1 and removed the include but still having problems with sending a SMS. I am sure it must be a pin-connecting problem - somehow I must have misunderstood the pin configuration ?. So -like kamillo1888 - I would love to see a clear picture/description of how to patch pin 18 + 19.