Would ask the manager to deal with it (that was their job) and they just went "no you can deal with it, that's your job to do". Ended up almost being bashed once.
I just keep calm and try to give understanding instructions
When a customer is arguing with you, the best option is to listen and remain calm. If the potential return has a valid reasoning behind it, then you can offer the return to keep the customer happy. If not, calmly explain why the return cannot be done, and whether they would like a complimentary meal, snack or drink, instead.
Attend the customer's concerns and problems, and try to solve at the earliest.