I want to dispute an Apple Pay charge

Then your issue is w/ QT who rung-up an incorrect transaction amount … which you must have subsequently approved w/ biometrics.

Similar situation as “Hey … I gave you a $20 … you only gave change for a $10.”

If QT won’t cooperate, you can then elevate the dispute.

See “How to dispute …” near bottom of this article:

Send and receive money with Apple Cash - Apple Support

Link-> Get a refund for purchases made with credit or debit cards using Apple Pay - Apple Support