Hi,
I work for a service and repair company, I forward the office phone to my cell phone 2 weekends a month, I answer calls and dispatch technicians... I am an hourly employee, but do not get any compensation when I am on call on the weekend, is this legal?

No it's not legal. If you are a salary based employee then that set up is legal. But then again, it may depend on your state laws. Check to make sure.