Minneapolis Overhead Garage Door Service Overcharged and Charged double what I was told over the phone Eagan MN

I called because my spring broke and I couldnt get my car out of the garage. I asked how much to exept the cost would be for the repair. I was told about $400.  

hey came out the next morning and he told me that the spring I needed would be more expensive then the one he thought it was the night before but he would give me this and that discount.  It seemed rather expensive but I needed my car out and he was giving me these discounts.

When he was done, he told me that the cost was $967! I didnt know what to do because he had already done the work. So I paid it. I called around and was told my a couple of comapanies that I was charged double what I should have been charged. 

I called Overhead and they said that since I signed it and paid for it, there is nothing they would do for me.  I got scammed for about $500. Do not use this company!!!!