Price increase of almost 45% on refill coffe

I was shocked to get a refill coffee with my car mug at Furrow road Equestria Wild bean cafe that is usually R8.90, and was charged R12.90. I thought the lady that took the order made a mistake and maybe charged me for a latte or something else. I queried the price and she said there was an increase. There are no info anywhere in the store indicating a price increase. The price board with the prices of the hot drinks that usually hang above the counter were blank. And it went up overnight. I am sure monday 04/05/2015 it was still R8.90. I don