We were subcontracted by the EC to install a fire alarm system and our SOV and AIA reflected both design and permitting costs. The fire alarm system contract was nullified by the owners after they were required to also install a fire sprinkler system. They instead awarded our fire alarm contract and the sprinkler contract to a new subcontractor. We designed, and permitted the fire alarm system which was approved by the fire marshal, however now the owner feels as though they were "overcharged" for these services, and want to regain monies already paid. We properly submitted both SOV, AIA and submitted progress payment lien waivers that were notarized for each requested progress payment . Lastly we were never paid roughly $4,200 in retainage for the design and permitting costs as our contract was cancelled. Do the owners have the ability to recover money if they feel they were "overcharged"?