Have a groupon deal then dont accept on arrival?

This above mentioned vendor had a deal on Groupon for a tea which I purchased as a gift for my mum. On arrival my mum was told that they had decided that despite the Groupon being issued that they no longer wanted to accept Groupons and cancelled the deal. What a joke and a waste of time. I would NOT do business with anyone that does not honour their agreements like this.How embarrasing as this was a gift and my mum had already traveller there. She said it looked dodgey in anyways. STAY AWAY!