Hey all, I want to dispute a charge on my credit card, but don't know if it's justified, please let me know. Here's the situation:

I went to a club last weekend, and spend $38. I noticed that the menu said that minimum charge is $20, and all charges will have 20% gratuity added. Firstly, I don't know how I spent $38, I only got 2 things of Guinness. Anyway, I get my check at the end of the night, and I see $38, which I thought was a little much for two beers, but I thought that they must have added the 20% gratuity on it already. So I left the "tip" and "total" blank and just signed my name on the non-itemized receipt because I was in a rush to leave... Yesterday I check my Chase card, and I see a charge for $45.60. Which happens to be $38 * 1.2.

Do I have the right to dispute this charge?