Do you say my AMEX, my Visa Gold, my MasterCard to mean your credit cards issued by a relevant company?
I always take (my) Visa Gold, when I go abroad on holiday.
Will you accept AMEX (at a gas station).
A more general term you can use for all credit cards is to ask "Do you take plastic?"
I have heard it used as simply Visa or Mastercard when refering to the credit cards.
A merchant can and has said to me on numerous occasions:
We accept cash, check, and Visa.