You have done well in creating this awareness here, though according to what you explained, it was more of trying to play a quick one on you, but you were smart enough or not careless, if not you would have fall prey to that cheap scam.
I have seen someone defrauded in my presence through pos because she was feeling pity for the customer, not knowing that the person want to scam her.
The person tried to initiate a transfer, showed her, her name in his phone, canceled it, and the next thing he showed her transfer completed,  she didn't know that the person canceled it.
After waiting for like 10 minutes she haven't seen the money, the guy was faking a call that his wife was about to put to birth, that her water has busted and it's the money they are waiting for, so out of pity, this girl release 30k to this scammer thinking that the money will later drop, uptil now, that was how she lost 30k, so if you are doing pos business or anything that involves money, try to be very attentive to every details if not you might be scammed in the process.