Refusal to change date (***0)

I recently purchased a groupon to go watch a T20 match. The tickets are sold for the 22 or the 29th of Nov (they advertise the groupon for both). When you click \buy"you select one of the dates and the qty. I accidently selected the 29th and only realized it when I was sending a request for the issuing of the real tickets. The person issuing the tickets said that she couldn't issue tickets for any other date than what is on the groupon. So I emailed groupon to ask if they can please just change the date on my groupon. They keep on saying that they cannot do it due to their bad system and that if they want to do it they would have to first do a refund then I would have to buy new tickets"