Dunkin' Donuts

I went to Dunkin Donuts (Tremont St, Boston, MA) store on 12/26 evening around 5pm to buy a $20 gift card. But I waited for over 10 minutes after the cashier swiped my credit card and still can't get my gift card. Something wrong with the computer system I think. The cashier was on the phone and trying to call somebody to fix the problem I think. There was a long line behind me. I didn't want to wait anymore and didn't want other people to wait because of me either. So I asked them to refund $20 to my credit card. The girl there told me that they can't refund $20 to my credit card now and I have to come back next morning to see the manager to pick up my $20 gift card. I said I don't have time to come back next day and I just want to have my money back to my credit card. The girl told me she can't give my money back and didn't explain why. And just told me to come back next day to see the manager to get the gift card I bought. The manager will be in the store from 6am- 1pm. Then I think it's ok to come back again. So I asked her to give me a receipt and she refused. I said there is no proof of my purchase and how I get my gift card next day. The girl said she can't give me a receipt and didn't explain. Then she let me write down a note on a piece of paper such as " I pick up my $20 gift card". I let her to sign the paper, but she refused. I insisted somebody to sign it. Then she asked another girl to sign. I was completely confused. I didn't understand what's going on here. She didn't explained anything to me. I didn't want to bother and just think I will come back tomorrow and everything will be fine. I came to the store next morning and asked for manager. A lady asked me why. I showed her the notes I wrote down last day. She said " oh, the system down yesterday. Your credit card was not charged. If it got charged you can call617-464-3796 ext 306. " I said " the girl told me yesterday that my credit card already charged and let me pick my gift card today. " The lady said " did she give you a receipt?" I said no. because she said she can't give it to me. I don't understand why. Then the lady said she is sure that my card was not charged. All Dunkin Donuts system was down yesterday. Just call that number if credit card got charged. So I believed her and bought another $20 gift card. But today 12/31 when I checked my credit card balance, it shows that they charged me two $20. I am really upset now. If the system got a problem, they should explain clearly to me.The cashier and the manager told me completely different things. And now I have to spend my own time to call that number to get my $20 credit back to my credit card. This is not right.