Dunkin' Donuts review: Charged twice and worst service

I’m a college student at The University of Illinois at UC so I go to the dunkin on green st. I’m waiting in line and the first red flag is that the customer in front of me seemed to be arguing with the workers for a long time. She told the worker that she has class in three minutes, so she just wants a refund, and the worker wrote something on a receipt and told her to come back at 3 instead (I guess she doesn’t know how to give out refunds?). I order and wait for fifteen minutes. A worker comes up to me and asks me what i’m waiting for and I show her my receipt. She told me in a impatient tone that the register didn’t accept my payment because of issues, but I couldn’t understand her since she has a very thick accent. I asked her to repeat stuff nicely because of her accent and she was pacing around. She explained it, but added “do you understand?” here and there very harshly. I told her I did and went back in line to order and pay again. I tapped my card once, but the cash register told me to tap it again. I told him that I already did and he groaned and told me to just tap it, so I did. I got my order and checked my bank app since I know that the workers have limited capacity and confirmed that they did charge me twice. I want a refund, and hope that they teach the workers how to work the technology and speak to customers better.