My garage door was installed about four years ago by a garage door contractor worked great till now the tenshion spring or whaterver seems to be having a problem at the top of the door is the rod with a spring and at the end is a weel at both ends the cable that goes around the pully keeps coming off so the door won't work what do I do

Look at the spring around the torsion bar. It most likely has broken. If so it will have to be replaced. Should have door technician do this as it is a dangerous process if you don't know what you are doing.