Assistance on GPS tracker project - SMS function

I need your assistance in correcting my code for a GPS tracking device. The sketch performs 3 functions

  1. Get GPS cordinates
  2. Post the cordinates to a server
  3. Turn on/off/ engine (led) and send gps cordinates using sms commands.

The first two functions work flawless and the 3rd works standalone. However, when I combine them, this happens: The sms function is ignored..and when it's run, there's a buffer overflow of that sort. I've tried several combinations but it doesn't work. It sometimes prints out everything but not in a way to allow the sms characters to be checked and compared.

Cross post from