I have a inexpensive singer, and my walking foot works just fine on it. I do not have an adjustment for the pressure on my presser feet either.
The sales person sold you the wrong foot for your machine, or could you possibly have it installed incorrectly?
I might take the machine, power cord, some scrap fabric and the walking foot to where you bought the foot, and ask what is wrong with this picture :wink: and try it out before you leave again :D:D:D