I’d keep things civil and respectful. At the end of the day, they’re only people who are trying to do their jobs and misunderstandings can occur. Plus, they’re less likely to wanna help you to the best of their abilities if they find you’re being rude.
To piggyback off of what Hellchaser said, I actually went through this same issue in November. After a few email exchanges, I provided proof from the artist stating that I was allowed to use the piece for my episode cover, so the support agent happily approved the piece for me. Definitely take that route & it should be resolved fairly quickly.