how to stop washingmachine filling with water even when off?

If it's twin fed [Hot and cold] check both solinoids are closing turn off the water to each one in turn to find out which one isn't closing properly, then replace the faulty one.
As for emptying it could be a blockage in the pump.
Of course the other thing is if you put added details like it's model ???? and top or front loader then some one who's got one and had the same problem might give you the solution.

Rob
October 2005