Wild Woolly's Saloon

Review: So I drink and buy rounds of shots in celebration of my friend's birthday. At the end of the night I used my card to pay my tab. My bill was $83. I was thinking Ok it could be possible. So I write $12 for the tip. My friend comes up to the bar and asks why is my bill so high. 1 of the 2 bartenders shows me a note pad with tally marks saying I ordered 15 vegas bombs which I knew was incorrect. I'm already being rushed out by the security. So originally I had the total on the receipt as $95. I crossed out the total and put $83 because me and my friend knew I didn't have that many shots especially when it was $2 well drinks and $2 shots. So days later my account still showed the $95 charge. I called the bar and talked to the manager because the owner wasn't there. Which, surprisingly, it turns out that it was the manager and owner working that night. So the manager told me she discussed my bill with the owner and that I did have some of the well drinks and shots even though they originally told me 15 vegas bombs and showed me a paper with tally marks on it with no description of my drinks, so of course how would they know the correct amount. So moving on to the tip they took even though I didn't want to tip them at all. So supposedly there is a sign behind the bar saying if your tab is over $50 they will charge a 15% gratuity. I've never heard of a bar doing that and how would I know that it wasn't included with my tab because of the tally marks and no description. Plus my tip I had on there was over 15% and they sure took the whole amount even though I crossed out the total on the receipt and put the tab of $83.Desired Settlement: I would like some type of refund because of their business ethics. Is it even legal to have a sign saying there is a 15% gratuity charge for a bar? Is even legal to take a tip from receipt when I crossed out the total? They can at least refund my $12.