I work for Verizon Wireless as a sales rep, and by far the worst thing ever is dealing with angry, older customers who will not take no for an answer.

I just got done helping a nearly 70 year old lady pay her bill through the IVR, and she was adamant that A) she came and payed her bill with me last month (not possible, as I was on vacation on that day), and B) that we credit her the entire bill amount because we failed to processes her non-existent payment. 30 minutes and a call to her bank later, and we confirmed that she had never made a payment and that she never mailed one. Of course, this was still my fault in some strange way and she was still expecting me to pay her bill for her...

God, I hate older customers.