Plumbers dont usually try and fix pumps. This is a good example why.
15 to 24 PSI? Hello?
Stop payment on the check and find a PUMP AND WELL guy that can perform actual, practical work. Or an electrician that is also a mechanic and contractor.
Not only have you been screwed by lousy work, you likely have no water in your well anyway.
Hey! Lets get the auto shop to change the muffler on your car before they BOTHER to check that the motor is blown, the tranny is shot and there is no oil in the crankcase.