False advertising and a *******

I'm so disappointed in the lack of communication with mugg and bean Northgate, I went in for my usual Cappuccino and ****in deal for R49. 90, I usually go to mugg and bean when I want to sit in, so I decided to go for that, only to realize I was charged R58. 80 for everything, only saw this when I got home, as I paid using my card and tipped the waiter R10, how is that possible when the menu clearly states R49. 90 I want an explanation for this.