If you're at all concerned about a merchant, always pay with either a credit card or by check. You can stop payment on a check or do a charge back on a CC.
I had the local Nissan dealer change the timing belt, water pump, etc. on my Pathfinder. I went to the cashier to pay the bill and noticed a $25 charge for "environmental compliance."
When I asked about it I was told that it was because they had to dispose of the old antifreeze.
I politely told them that wasn't my problem, it was part of their shop overheard. They could remove it and I'd write them a check for the service, or they could dig in and not give me my car unless I paid the whole amount.
At which point I'd be "glad" to write them a check for total invoice, which I would call and stop payment on the minute I drove away. They could then take me to small claims court if they wanted to get it all sorted out.
They pulled the $25 charge.
The lesson is - some people will try to cheat you but they can only do it if you let them. And they're much more likely to try to cheat people that they think are easy marks. Once they see you aren't, they'll probably back down.
As far as the BBB - Backing Bad Business for decades...