After the free trial, consumers who no longer wish to receive the monthly supply must cancel their subscription or be billed $40 monthly. Some customers complained of a 75-minute hold time on calls to the company. Others said unauthorized charges were made on their credit cards, according to the bureau.
An automated operator from Central Coast Nutraceuticals told ABCNews.com that "due to the popularity of the product, there are unusual hold times -- 38 minutes."
The Better Business Bureau provided ABCNews.com with phone numbers for FX Supplements and Central Coast Nutraceuticals that matched the phone numbers the companies had posted on their Web sites. Both numbers placed callers into long delays with automated messages.
In December, when asked about the company's business practices, Braybon Spier of Fit Factory, Central Coast Nutraceuticals' partner company, told ABCNews.com that people don't read the "fine print" when placing their acai orders. "But we do have a lot of satisfied customers who have lost weight. I personally use it myself."
The Better Business Bureau says buyers should beware of these types of practices.
"Dozens of companies across the country are doing the same thing," bureau spokeswoman Alison Southwick told ABCNews.com. "Maybe they are selling juice instead of supplements, but it's similar kinds of sales practices."
Annual sales of acai products exceeded $15 million last year, up from $500,000 in previous years, according to the bureau. The so-called "super food" has been praised for its antioxidant properties on television shows and on social networking sites, with some claiming it fights cancer, aging and weight gain.
In November, according to the bureau, more than 1.5 million people searched for the term "acai" on Google. Online ads and Web sites often include a photo of a celebrity -- such as Winfrey -- and falsely claim that she endorses the acai as a weight loss miracle.
While the acai's nutritional benefits have been mentioned on the air frequently, the berry's alleged ability to aid weight loss has often been misconstrued in these ad campaigns, according to the BBB.
Columbia University heart surgeon Dr. Mehmet Oz, who appears on "The Oprah Winfrey Show" as a medical expert, told ABCNews.com that he had never officially endorsed acai.
"Acai is a powerful antioxidant," said Oz. "Colorful, dark foods like red wine, pomegranates, concord grapes, blueberries -- they call them brain berries -- are full of nutrients."
As far as those weight loss properties, Oz said, "I'd be surprised if by itself acai could help."
Harvested as a deep purple pulp from 60-foot palm trees, acai (pronounced "ah-sigh-ee") is exported as a thick pulp and sold in a capsule, powder or juice form at health food stores and online.
Acai products are distributed through such stores as Whole Foods, Wild Oats and Jamba Juice, as well as many conventional grocery chains and the Web.
The berry was virtually unknown outside the United States until 2001, when brothers Ryan and Jeremy Black began to sell acai through Sambazon Inc., promoting its antioxidant properties.