Handout photo.

Not every agreement with a big-name company is a gem—a lesson South Florida jewelry stores claim they learned the hard way.

A group of jewelry companies filed an $18 million countersuit against Swiss watchmaker Ulysse Nardin after the company accused them of not paying their bills. Ulysse Nardin is owned by Kering, a publicly-traded Parisian company that boasts annual revenues of nearly $15 billion and a portfolio that includes Gucci, Yves Saint Laurent and Balenciaga.

The watch manufacturer sued Boca Raton businessman Bobby Yampolsky and five of his companies earlier this year. Yampolsky negotiated authorized dealer agreements with Ulysse Nardin on behalf of jewelry stores in Boca Raton, Palm Beach, Miami, Sunny Isles Beach and Aventura, according to the watchmaker’s complaint.

Ulysse Nardin sent the stores watches, bracelets, straps and buckles and performed repairs—but the stores became “grossly delinquent” in paying for the merchandise, to the tune of more than $2.7 million, alleged the lawsuit filed by Eric Rosen and Alexandra Tifford of Fowler White Burnett in West Palm Beach and Wayne Dennison of Brown Rudnick in Boston.

The defendants hired Fort Lauderdale attorneys Bradford Cohen and Michael McMullen of Cohen & McMullen. Cohen, who appeared on “The Apprentice,” has represented the Trump Organization and a slew of athletes and musicians including Dennis Rodman, Vanilla Ice and Udonis Haslem.

He painted a different picture of the stores’ situation: They spent at least $3.6 million on pricey lease agreements and store setup and then had trouble recouping the costs because agreed-upon prices were undercut by Ulysse Nardin, according to the allegations.

The stores offered watches at the manufacturer’s suggested retail price, as required by the agreements they signed, the Oct. 6 fraud countersuit alleges. But they soon found other retailers were selling them for less.

The jewelers “effectively became advertisements to promote UN’s products,” the lawsuit claims, because customers would walk into the stores and try on watches, only to buy them elsewhere.

“UN and Kering should be ashamed of their totally reprehensible behavior,” Cohen said in a statement after filing the Oct. 6 countersuit.

Rosen did not immediately respond to a request for comment.

The case is before Palm Beach Circuit Judge Edward Artau.