Franchises are a unique breed of business. They operate under the umbrella of a national brand, which means they all generally offer the same products and hold to the same standards. But they are also independent businesses allowed to make their own choices about marketing and whether to participate in promotions put together by the corporate office.

It’s a setup that can be perilous for consumers.

“Unlike normal transactions where there’s a company and a consumer, we’ve got a triangle,’’ said Philip Lowe, marketing professor at Bentley University. “By definition, that makes it a little more complicated.’’

A reader from Bourne experienced one of the complications after receiving a flier from an auto repair franchise. The mailer offered an attractive deal on any service over $399 and listed just one location — there was no indication that the location listed might not be participating in the promotion.

Yet, after paying $400 for a new muffler, the customer was told the shop wouldn’t honor the offer. The corporate office said the franchisee did not have to extend the deal, and it didn’t respond to my requests for further clarification.

Was the franchise owner’s action illegal? Possibly. Though it is unclear whether the mailing was sent by the corporate office or the individual franchise, the fact that only one location is listed makes it likely that a consumer would conclude the offer was good at that shop. Massachusetts advertising law states that “at all times a business representation should not be false or misleading; a merchant’s failure to disclose an important fact may be unfair or deceptive.’’

Regardless, it is essential for consumers to be proactive in protecting themselves when it comes to dealing with franchisees. First, always confirm that a deal, sale, or coupon really is being offered by a given location, even if it seems completely clear in the advertisement.

If you find yourself facing a franchisee who won’t honor a deal, try appealing to a manager’s business sense — a small concession now on his part might make you a loyal customer down the road, Lowe said. If all else fails, try appealing to consumer watchdogs, and let the store owner know you are doing so. To file a complaint with the Massachusetts attorney general’s consumer protection division, call 617-727-8400.

Have a consumer question or complaint? Reach Sarah Shemkus at seshemkus@gmail.com.