no heat mat for chameleons!!! Try upping the wattage of the basking bulb. They do not need the whole cage heated. They just need a place to warm up which would be the basking area. What kind of temps are you getting, ambient and basking?
Do you have a pic of your setup. Like Carol said no heat matt. I am curious are you using a tank, or how do you have a heat mat rigged up on a screen cage.
Chams dont secnce heat well from below hence why we use a basking buld replicating the heat created by the sun.
Hoj