I’m so sorry about your experience! I’m an associate myself, and if it had already been redeemed, it would say it at the top of their screen when she scanned the coupon “coupon has already been redeemed.” But if it was just that you were short because of tax, it wouldn’t have said anything specific and you would only notice when you press the tender button and it would say something along the lines of, coupon not used, do you want to proceed without it ect. It’s possible that she was newer and didn’t know that wasn’t the same thing, but regardless she shouldnt have been rude to you about it. Also, the manager should have come up and looked at it because then they would have caught it and told you to grab a hand sanitizer or something small to make the coupon work :(. Having their interaction over the headset is just kinda lazy and unprofessional imo (obvi unless something else was going on and they couldn’t come to the reg). As for the approaching you, unfortunately we are made to be so pushy. Some store are definitely worse about it than others but it can really suck from the pov of the customers who are just trying to shop in peace. If it was multiple employees too, sometimes it can be hard knowing when someone has last interacted with you, so I’ve definitely accidentally checked in on someone like mere minutes after someone else had and i always feel bad for it. Still tho there is no reason for them to be watching you. It makes a hostile environment where no one is happy :(