Thank you for your prompt response. Regrettably, it does not address my situation.
The merchant has offered only a phone number for payment, not a website. Tap-and-pay is not applicable since the merchant is hundreds of miles away and I'm not using an iPhone but rather an iPad without NFC support.
While the merchant has offered only a phone number, this is not a scam. I understand that the only way to use an iPad to send Apple Wallet money to a phone number is through iMessage - which is limited to Apple Cash and non-commercial transactions. That's not my situation.
From your response, I understand that there is no way to use Apple Pay on an iPad to pay a merchant with a bank credit card in Apple Wallet if the merchant has provided only a phone number. Am I correct that such a transaction can be done only through some Apple Pay link on the merchant's website which I will need to access through Safari?