I was taking the escalated calls earlier when I came across a customer who was at max volume even if my phone's volume was at half. She was asking for a refund, which I obliged, and halfway through she had the same sarcastic tone of which I reciprocated with, "look, I am trying to help you out here with your charges. I already told you I am going to refund them so please stop shouting at me." She retorted, "oh I'm sorry, I am hearing impaired, I wasn't shouting it's just that I cannot hear you and you are on speaker because my ears cannot bear the heat that the phone is producing."
I felt really bad about it and myself. I probably deserve this guilt.