Paying The Price For Not Being Nice

(I work at a children’s swim school as the front desk receptionist. I am on the phone with a customer who has called and wants to sign up his son. After setting up a schedule:)

Me: “Would you like to take a tour before you sign up?”

Caller: “No, I’ve been there before. My girlfriend’s son used to go there.”

Me: “Oh, okay and is [Child] your girlfriend’s son, too?”

Caller: “Yes.”

Me: “Okay, what’s the older son’s name? Because he’s been here before and they’re siblings, you don’t have to pay the registration fee.”

Caller: “Oh, no, the older one is not my son.”

Me: “Yes, I understand that, but you said that your girlfriend is the mother to both of the boys, so I can apply the discount—”

Caller: *interrupts me* “I told you that [Older Child] is not my son, d*** it!”

Me: “Okay, sir, I’ll add the $25 back to your total.”

(He paid the fees and I’ve yet to hear from him since.)