There's often a very good reason for asking to speak to a supervisor, Customer NO-Service. I understand that many customers have unreasonable demands, but you can't fall into the trap of assuming the customer is always wrong. A Service Rep should be trying to smooth relations between the customer and the business, not just keep repeating "it's our way or the highway". That may increase the SR's number of "problem calls solved" per hour, but it doesn't keep customers.
As a personal example from a few years ago, before online banking became so prevalent. I recieved a call at work on Friday morning from the bank that held my auto loan. I was told my loan was over 3 months in arrears and would be repossessed on Monday if I did not pay in full. I was confused since I had been sending checks and payment stubs regularly, and this was the first notification I had recieved that there was a problem. However, even after having my local bank rep call the loan bank rep who told her the checks were cleared and had the proper account number on them, the loan bank rep continued to say: "Well sir, if you had actually made your payments, it would show on our computer. Since it doesn't, you will need to come up with the full amount by Monday or your vehicle will be repossessed." This continued through many calls back and forth with me trying to generate some kind of proof that the rep would believe (the cancelled checks were stored at the main bank office and would take 5-7 days to be mailed to me). I could never get her to check for an error on the loan banks end. Finally, as the end of the business day was approaching, I finally managed to get a supervisor on the line and convinced her to actually check their records more carefully. As it turned out, the problem was exactly what I suspected was the problem but could never get the original SR to investigate. I had an RV loan at the same bank, and it had been recieving 2 payments per month for the last 6 months. They were apparently just going by the name and they were ignoring the account numbers on the stubs and the checks. Since the RV loan was older, it was the first account to appear on the system under my name. Once the supervisor finally listened to me and actually checked the records, it was obvious that it was their error. Once the payments were credited to the proper accounts, SURPRISE, SURPRISE, I was actually a month ahead on both accounts, which matched my records.
If the CSR had treated me with a little respect, the error could have been found and fixed in 15 minutes and been a minor issue. Instead, I was assumed to be a liar and a deadbeat. This caused a lot of wasted time and effort on both ends of the phone and made the problem much bigger than it needed to be. And it caused the loan bank to lose a customer, I refinanced both loans with another bank after this fiasco. Had I been treated as someone to work with in solving a problem, instead of acting like I WAS the problem, they would have still kept a customer and all that nice fat interest.