Car dealership owes me $750

I purchased a car 8/16. 10 day payoff when I signed sales contract was $15,600

8/20 or sometime around then a $750 credit was applied to my auto account. (It was from an extended service contract I cancelled a while ago)

8/29 the dealer paid off my trade for $15,600.

9/7 my bank issued a $750 refund to the dealer for overpayment

I’m trying to get my $750 back and not having luck

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I called the finance director somewhere around 8/20 and let him know what was happening. He said no worries, when we get the check we’ll send you one.

9/21 I emailed the finance manager to ask what was going on and when I can expect my check.

9/26 I called the finance manager, he “hadn’t seen my email yet.” Said he’d call the “warranty department” and get back with me in 30 minutes or so. He never called back.

9/27 I called him again in the morning. Said he hasn’t learned anything yet from the “warranty department”. I tried to explain this wasn’t really a check coming form a warranty company, it was straight from my bank due to overpayment. It was just bad timing when the credit posted to the account. He said he’d look into it and get back with me. Didn’t hear from him. at 3pm I texted the sales guy asking for the GM’s name/number/contact info. I get a call back from the finance manager saying “oh theres no need to get the GM involved and all that, we’ll just cut you a check and find out what happened with the refund they sent later”

10/10 still no check delivered to me

10/11 I call the store, ask for the finance director. He’s busy. So I ask for the GM. Leave a message explaining the situation.

10/12 I get a voicemail from the GM in the morning saying he’s “looking into it”

10/14 and I still haven’t heard anything. Maybe I’m missing something, but this seems pretty straight forward. They confirm they got the refund from my bank, then issue me a check. I don’t understand why it’s taken over a month to do this, and why each time someone “looks into it” I go days without hearing anything.
Monday I plan to show up in person to the dealer but I’m expecting to get the same “Oh we haven’t heard anything yet, we’ll let you know” that I get every other time.

I’m very frustrated because imagine this scenario went the other way, and my payoff came back $750 higher. The dealership would not be giving me over a month to “look into it” and it would be a violation of the sales contract if I didn’t pay the difference.

I made my down payment on a credit card, so I could try and start a chargeback, but I don’t think that’s the best option.

Do I need to give them more time? What are my next steps?