I have never come across that but I understand that some merchants are charged 2.5% for every transaction. My local family owned butcher shop requests a minimum of $10 to use a credit card. I try to get the cash out before going there because I know it is costing them money for me to use my visa debit card. The money is in my account I just can't be bothered most of the time to go to the bank to get it out. If businesses were smart, instead of saying they are charging a fee to use a CC, they should offer a discount for paying with cash.

It's against the standard merchant agreement for them to charge you more for using a credit card, though they can discount for cash, which winds up being the same thing. The difference is that more people will use their cards if it's stated as cash discount rather than penalty for using a card. It's the brand of the credit card that determines whether a merchant will take it, not the co-branded loyalty sponsor. Most clearinghouses will take MC, VISA, AmEx and Discover interchangeably, nowadays. For low volume businesses, like the mom and pop store, their local merchant bank may still only take MasterCard and VISA, but there are many alternatives. In the old days, you had to submit to each one separately, and it was a bother, but if you're big enough to have a terminal, you can send them all to a clearinghouse for processing. And if you're tiny, there are a bunch of vendors, such as PayPal and Square, who charge a higher discount and far lower minimum, and take all the major cards. I've never had any trouble using a non-Costco AmEx at Costco, and I'd be mightily surprised if Sam's wouldn't take a non-Sam's MC, as is borne out by the page Chi83 linked. There would be no upside for MasterCard to co-branding if their other cards weren't accepted. The difference is that you don't get the Sam's loyalty points they give you for using your Sam's card when using a different MasterCard. The employee you spoke to may have misspoken (said the wrong word) or been under trained. It has to be MasterCard (or Discover) and not VISA or AmEx. Really big sellers make special agreements with the credit card companies to only accept their cards, which is why no VISA. And why VISA always advertises that the Olympics doesn't accept American Express. They throw their weight (and money) around to get exclusivity. Which is why Sam's would be screwing it up if they only took the Sam's labelled MasterCard. You said "apply" however. You probably can only apply for a Sam's MasterCard at Sam's. You can get a plain MasterCard at your bank, or choose from any number of co-branded cards from other stores, organizations and institutions.

There is no "way" to do it, it is simply a matter of whether a vendor takes cards, or not. We did once buy a Lexus SUV on a credit card, all of it, but that was a one time promotion with the dealer and Amex. The vendors pay a fee. The fee can vary greatly, usually the more business a vendor has the lower the fee. In day to day transactions with very large companies, the fee is invisible. (in fact generally most card agreements prohibit differentiated pricing, otherwise there would be no credit card business). With a proprietor, it is very much visible to them. He will probably do it if you paid the fee but, guess what ... the fee is going to be more than the value of the miles. I might only do this if I were very close on miles to a trip I wanted, and it was cheaper than buying them. Usually, the most economic thing to do with a sole proprietor is to pay cash ... no fees... and hey, I don't file the guys taxes.

We had a disappointing experience with Amex. It was charged with the purchase of a very expensive large TV from an internet store in Italy! The card is rarely used and had not been used for a year or so when the charge was allowed through. It should have been flagged immediately and blocked but it was not. It appeared on our bill. We notified them immediately and requested it be removed immediately. And why exactly did it happen in the first place. They did not agree to remove it immediately. They had to do an investigation! A purchase for a TV in Italy delivered to a place in Italy! That made no sense at all. It took a month or so to finally get them to remove it. I mean the TV had to be delivered somewhere! Follow the TV! It really soured us to Amex. Their employee agreed it should have never made it to our account.