I have had a very similar experience to others on here with groupon. I bought a voucher off them and when I went to redeem it, they added another voucher to my cart then charged me automatically. They now refuse to refund my money even though I have stated it was their error.
Further, the voucher they charged me for is not the voucher they have sent me, so I have been over-charged and not even received the actual good I bought.
Customer service is terrible. All done via email although I have asked for a phone number many times to speak with someone direct.
I will not use groupon again and will urge all my friends not to use them as this has been so frustrating, first having been swindled by them and now having to deal with their customer service. The money you MIGHT save if they don't cheat you is not worth the probably chance they will.