DAYTON BOAT STORE INC

When I dropped off the boat (21 foot Searay), I was told tuneup would be about $250, agreed to cleanup/buff of $200-$250, and asked for new tires and to repair taillight on trailer.  Although was told low amount, I expected to hear would need new batteries, so although I didn't say anything a the time, I estimated total bill would end up around $1000.  Was promised they would look at it and call me mid-next week to get authorization before doing any work. 
At end of next week, I had not heard from them and called them.  They still hadn't looked at it.  Promised to look at it next week and would likely have it ready before the next weekend (August 9-10).
End of next week, called them again because I still hadn't heard from them.  They said they were running behind and hadn't looked at it yet.
Finally heard from them on August 14th (original drop-off date was July 26th...).  They said they needed to arrange to haul off bad gasoline ($15/gallon so estimated could cost less than $300) and rebuild the carburetor, and batteries wouldn't hold charge.  Still needed to do the tires on the trailer.  When I asked how much this was going to cost me, he told me "about $1800".  I gulped and said ok.
When I picked up the boat on August 20th, the bill was $2950+!!!  He argued with me, saying that the $1800 was the total at that point when he had called me on the 14th and there was still the carburetor to do, etc.  I was also charged nearly $400 for the clean-up/buff and nearly $500 for the gasoline to be hauled off.
I was never given an opportunity to authorize all this work ... I would have said NO!!  The only call I got was to ask if I wanted the boat cover repaired for $250 or replaced for $850 .... I said neither, that I would repair it myself.
We are currently disputing the total through our credit card company.  Terrible communication with their customer and did unauthorized work (cello