Once a week, every week, Wayne Sorenson gets a phone call that he knows not to answer.

Sorenson checks the number and lets the call go to voicemail. He may not know who it is, but he knows it likely is an agent offering to sell his timeshare.

The 70-year-old Columbia Heights man and his ex-wife have owned a timeshare in Branson, Mo., for 30 years now. His family enjoyed it at first, but Sorenson said they no longer use it and want to sell. For three years they have tried to sell the property. Each year they have met roadblocks.

Terms of their timeshare contract make it difficult to give up ownership. Maintenance fees cost more than $1,000 each year, despite the family not using the property in about a decade. And Sorenson doesn't trust agencies who call him each week, explaining that many ask for thousands of dollars without a promised buyer.

So when a business called We Finance Co. called saying they have a buyer who will pay twice what Sorenson first paid for the timeshare, he felt hopeful. Sorenson had exhausted many options, and an attorney who reviewed the company's contract paperwork told him the business looked legitimate,

But after weeks of negotiations and $8,950 spent without a deal, his hopes soured.

"I'm yelling at this guy, swearing at him, calling him every name under the sun. And I said, 'Chief, you messed with the wrong boy,'" Sorenson said. '"If you're legitimate, I am going to be the biggest thorn.' ... And I said, 'If you're a fraudster, you better get the hell out of the United States because not only me, but everybody that I can get is coming for you."

A new study by the Better Business Bureau shows consumers have filed more than 20,000 complaints about timeshares and vacation clubs from across the nation. Lax enforcement and consumer protection laws have led to scams that cost customers more than $3.5 million, according to the study. Officials believe that's an undercount.

"It happens to anyone and everyone of all ages, all socioeconomic backgrounds, all races, all genders. ... What we're seeing is just the tip of the iceberg," said Bao Vang, vice president of communications at BBB of Minnesota and North Dakota. "There are people who feel really ashamed about losing money or almost have lost money and [are] feeling duped or being duped. ... They don't choose to share their experience."

Some of those victims could be Minnesotan.

Sorenson called the San Francisco Police Department and asked them to check if the business address is real. A responding officer found a locked and unmarked building with no one there to answer. Sorenson filed reports to his bank, the FBI, the Federal Trade Commission and the BBB explaining that he may have been scammed.

The BBB researched the company, finding that it was not listed on the California Secretary of State's registry — a sign that the business could be illegitimate. They told Sorenson they would continue investigating the matter and advised him to stop wiring money.

We Finance Co. did not return requests for comment at the time of this article.

"I was impressed [and] hopeful that there could be a resolution to this at some point before I die," Sorenson said. "Because I've got a feeling this is going to go on and on and on and on, and they're just going to hope that my memory fades."

Despite those efforts, Sorenson may never recoup the money he spent trying to sell that Branson timeshare. Many more people may be in his shoes.

A scam tracker tool that collects reports sent to the BBB says that at least two-dozen timeshare scams were reported by Minnesota residents. Some said they lost nothing. Others reported losing tens of thousands of dollars. One Minnesotan reported losing $92,000.

To prevent future scams, Vang says people should share their experiences and raise awareness for others.

"Education is one of the very best ways that we can stay informed about our marketplace and prevent additional and future fraud and scams," Vang said. "We want [consumers] to work with us at BBB so that we can help you understand the situation and all the promises there are, and the promises that are just too good to be true."

Her advice to those considering a timeshare: Research the company and its contracts. Check reviews to verify if others have had bad experiences. And if you believe you've been scammed, report it.

If you ask Sorenson about timeshares, his advice would be to stay away.

"You shouldn't be buying a timeshare," Sorenson said. "They sound good and fancy ... but when you own that timeshare you own it for life - not only your life, but your siblings [and] your kids' lives."