Rude drive thru customer

Tdy I got a customer who asked me for the price of their meal after they alr paid so I said I couldn’t do it. They insisted on getting a manager and it got super heated so I had to run inside to get one. The dt line was also very long and they were holding up the line And cars behind were honking. Afterward I had like five cars demanding what took so long

Obviously I could’ve dealt with this better but since I’m new, I’m wondering how I can deal with situations like where a custumor asks for a manager at drive thru to avoid it affecting others