Toilet tank does not fill up to it's capacity, which does not flush all the waste down. Have to flush two and three times before it's gone. Please help, I'm wasting gals. Of water all day every day

The ballcock should be adjustible via a screw on top of the unit. If its just a brass rod with a float you can bend the rod slightly up to raise the water level. The correct water level is about 1" below the top lip of the refill tube.