The examples which are included with the GPRSbee library are a bit out of date. This mainly relates to the intialisation process.
This should work for initialisation on the Mbili:
gprsbee.initAutonomoSIM800(Serial1, -1, BEEDTR, BEECTS);
The old method of specifying which switching mode to use has also been removed.
Also, you might have issues with using the 1.6.5 version of the Arduino IDE as that version is several years old now. Additionally, make sure that the version of the Sodaq AVR board files is up to date.