Need to contact Apple Pay Support Desk

No such thing exists.

You can call Apple Support directly or your banks / card issuer's support help desk.

click here ➜ Apple Pay Support - Apple Support

or here ➜ Apple Support World Wide phone numbers

Phil is 100% correct!

Apple Pay is a service banks choose to participate in or not. Banks pay a .01% of each transaction, but bank customers gain increased convenience, security, and protection from fraud. Banks and Payment Network Operators (Visa, Master Card, American Express) have IT support from Apple engineers.