Business ProfileforWolff Mechanical Inc

Date Of transaction was on Aug 30, around 4:30PM I received a bill for $1100.00 I called up Wolff and they explain what this bill was for. One replacement for the new Motor and a *************** I told them that for 4 days after they left the replacement, it was not working so I call a new AC guy and he told me that the wire was hook wrong and that why it would not work.The service guy that come out the first time told me that I might need a new motor I asked him how much he said $495. I said ok. So when I got the bill for $1100, I ask and that me it was for a new motor and the ***************** That when I said well it has not worked since you left the rescue motor. He then told the bill down to $750. I them send them the bills I paid to fix their mistake so they could take it off and have not heard anything about it. I just got a bill for $750, so assumed that they will not take all the extra 250. I spoke to the sales manager and he seems to be not wanted to help. So what is my next step? I am a Senior and I am on fixed income and feel they were trying to take advantage of this.