PetSmart — overcharging/hanging up on me when I tried to get information for filing a complaint

I’m writing in regards being overcharged for my services for the grooming department. I have taken my dog to the groomers at petsmart for a number of years. But today for some reason I was charged $70 for a service that usually cost me $48. Plus for some reason my dog is shedding everywhere. When I called to go over how much everything was the manager amy told me everything should of come up to $48 when I asked her why they charged me $70 she put me on hold came back and basically told me that we signed a paper at the being telling us what we could get charge. I called back to the store to try to get information on how I could complain to corporate and the store just put me on hold until I hung up. Very dissatisfied with my service and how I was treated on the phone.
I would like petsmart employees to fairly charge people and for the managers to be able to fully explain their employee actions.