Factory Alarm/Auto Start

Hey guys,

Just wondering if any of you have a 05 Mustang with the factory upgraded alarm and remote starter. We've been told we can't use one key fob for auto starting the car and setting the alarm on the car. I can't believe this which is why I'm asking anybody else have this problem?
 
My GF's car has autostart, but it had to be added aftermarket. 1500!!!

She uses her chevy fob, and presses lock 4 times to autostart. Lock again to turn off the car.

Can't get that on mine tho, i have a manual drive.