Re: Plywood sub floor
I agree with Peter, this should have been mentioned by the installer BEFORE the floor was laid so that you could have addressed it then. Now you're either stuck with an uneven floor OR the expense of tearing it out and replacing it, just so you can level out the subfloor.
As to the subfloor, without knowing what is under there and causing the unevenness, it is difficult to say whether replacement of the subfloor is necessary OR if it could be overlaid with underlayment or even floated out with floor leveler compound.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!