S & R Towing overcharged, charged much more than estimate Oceanside California

I called several tow companies to tow a 20 ft. container.  I got various quotes, and chose S & R due to the proximity of the pickup, and their low, but not lowest, rate of about $200-225.  The tow operator was very courteous and efficient, but it was only his second container; his first was moved about 100 feet at a construction site.  When delivered, he called in for the invoice: $350. I complained, of course.  I had previously spoken to Chris, several times, now I spoke to David.  He basically said that if I don't pay, they will impound the container and store it in their yard, and I would have to pay the $350 plus the storage fee. Of course, I paid, as I didn't know what else to do.  I later spoke to the general manager, who assured me he would look into it and get back to me.  This happened about two weeks ago, and I'm still waiting.  I wouldn't want anyone else going through the same experience I did.