How do I dispute on Apple Cash.

I purchased an Apple Watch from someone and I paid with Apple Cash which is link to my debit card. nobody sent me the item and I asked my bank to dispute the money but they said because you paid with Apple Cash you need to follow up with “ Apple Cash 1infiniteloop” to get your refund. I don’t see any option or how is the process. Could you please how can I dispute the money and get the refund?

please help me with that.

Thank you