On the credit card subject, I had quite a few places that said my credit card was 'Declined'. I gave them another and another and they were all declined.
I even called Capital one in there presence and Capital one had no record of the merchant even trying to process a charge. I think some of the merchants say it was declined in order for you to pay in cash.
I believe they try to run it as a debit, skip the pin and it shows up declined.