Groupon, the one deal a day group coupon site, is so popular that some people pay up front and then have trouble.

Channel 2 consumer advisor Clark Howard heard from people who say it’s hard to cash in on their coupons.

James Greco needed lawn work, so he bought a Groupon.

“Every time I called they kept bumping me back. The first excuse was ‘Well, we have so many Groupon customers.’ A couple weeks later they said, ‘Well, we’re really not making any money off you guys, so you guys are a low priority,’ and they kept scheduling me, but not showing up”, Greco said.

Sheila Lindsey said a carpet cleaning company stood her up, and when the cleaners finally showed up, she was unhappy with the results. “I’ve called the company at least six times and each time I’m told that they’ll have a service representative or the general manager call me and no one ever calls me back,” Lindsey said

And Shelly Hutchinson bought a Groupon for gourmet cupcakes. She wanted to get them right away. But a store worker had bad news for Hutchinson.

“She told me I needed a two-week advance notice before I could get the cupcakes.”

Hutchinson said, “The biggest problem I’ve had with Groupons is you call and they’re so overwhelmed with Groupon that they can’t fit you in, they can’t give you what they promised, so I think that if Groupon put more thought into what realistically this company can do, then they might be better off.”

Groupon said businesses can put a cap on their deals, but many businesses don’t want to do that.

Clark Howard had some advice for people considering Groupon.

First, research the company. Check Yelp, City Living and the Better Business Bureau. Second, consumers should decide how quickly they want the deal. The smaller the business, the harder it might be to get a deal right away.

But what about customers who’ve already bought a Groupon, redeemed it, and are disappointed?

Clark said if the company won’t help, call Groupon.

That’s what James Greco did.

“Groupon was great”, Greco said. “I called them up and they offered a full refund of what I paid.”

Clark’s favorite alternative to Groupon is Scout Mob. It will tell you about local deals, and you don’t have to pay any money up front.