Unfair billing

I bought 10 of panama jacks specials on wiki deals each special was R295. When arrived at the place we bought drinks. The time we got our bill we were confuse as we had to pay a whole R400 prior to our bill not know they charging us 10% on the wikideals special as it did not state that on the t&c . This has never happened at any other place. Extremely disappointed as we would've given a great tip