not very professional/ bad attitude

I called nph elect for a quote on my geyser i was told they have to come out to see, which they did and proceded to change a thermostat and a isolator and a element no one said to that these need to be replaced they just went ahead with the job and presented me with a R1616.00 bill why in heavens name wound i have asked for a quote for that very reason as to how much my budget can afford. I f that was to high i surely would have gotten another quote from other companies. when calling the nph elect oh heavens how very unprofessional.Oh and that night hot water was pouring out of the geyser i was told a faulty thermostate, which they did replace i have had many a homes i have owned replaced thermostat and never have had faulty products.I have offered to pay this bill off and they refuse. they say i am trying to get out of paying a bill they need to be taught a lesson to conduct business in a honest manner.and a understanding professional manner.