When dealing with a less-than-helpful customer service representative, consider turning into a broken record.
"I understand that is company policy, but I'm not giving up until ..."
Fill in the blank with "I get a refund," "I get a credit," "We come up with a better solution to my problem" or whatever it is that you are seeking.
A key phrase for emphasis is "I'm not giving up until..." or "I'm not going away until..." And remember that a supervisor often has more power to make decisions or changes than an underling.
For example, a few years ago, I needed to consult a medical specialist, and my insurance required me to see an in-network doctor. I checked the insurance company's website, I called the specialist's office and I called the insurance company.
Everything I looked at and everyone I talked to indicated this specialist was in the insurance company's network and it was okay for me to make an appointment.
After the appointment, the insurance company refused to pay the bill, because the specialist was not in my particular sub-network of local doctors. The specialist's office said it had been my responsibility to determine in advance whether the appointment was covered -- never mind that another person in that office had previously told me yes, they accepted my insurance.
So I called the insurance company again, and started playing my broken record. After four or five variations of "I want you to pay this bill," the young girl said, "Let me get you my supervisor."
When the supervisor came on the line, I told her -- quietly but firmly -- that I wasn't giving up until the bill was paid. There was a brief pause.
"Okay," the supervisor told me. "We'll pay the bill."
And they did.
The key is to stay calm, but determined. The other person is assuming that you will give up and go away, which is what many people do. Make it clear that you have no intention of backing down.
The interesting thing is, it usually doesn't take as long to get positive results as you might expect. Often the other person -- who may be talking with complaining customers all day long -- doesn't really listen to what you are saying at first. But the fact that you keep repeating your key phrase makes them take more notice of what you are saying.
Do you have a question on an insurance bill? Tight shoes that you want to return but store policy might not be in your favor? An item that was shipped to your door that arrived damaged?
Get on the phone or go to the store, and calmly repeat yourself. It can work.