The endorsements are also misleading, according to the bureau, and some lawyers representing those celebrities have already gone after these online companies.
"Consumers should be aware that Oprah Winfrey is not associated with nor does she endorse any acai berry product or online solicitation of such products. Attorneys for Harpo are pursuing any companies that claim such an affiliation," said Don Halcombe, spokesman for Harpo Productions, Winfrey's production company. Rachael Ray has also complained to companies that falsely claim she has endorsed their products.
Consumers can check www.bbb.org to get a "reliability report" on particular companies before purchasing an online product.
"These companies are simply abusing general acai berry endorsements from well-known, trusted celebrities by using it as a tacit endorsement of their company and products specifically," added the bureau's Cox.
"Consumers trust Oprah and unfortunately, if they are tricked into believing that she is putting her stamp of approval on a product then they are definitely more likely to purchase it," he said.
Two of the companies named by the Better Business Bureau are Central Coast Nutraceuticals and FX Supplements. FX Supplements offers a risk-free trial of products such as Acai Berry Maxx, for the cost of shipping and handling. However, if consumers do not cancel within the trial period they are sent additional bottles every month and are billed $85.90, according to the Better Business Bureau.
Complaints to the bureau in Fort Worth, Texas, showed consumers had a difficult time canceling subscriptions from FX Supplement via the e-mail provided by the company. In some cases the e-mail address did not work. Several consumers were forced to close their bank accounts or cancel credit cards.
ABCNews.com called FX Supplements at a number provided on the company Web site and received an automated message that said, "This number has been disabled."
Similarly, the bureau serving Central, Northern and Western Arizona has received more than 1,400 complaints for Central Coast Nutraceuticals. The company sells acai, hoodie and male enhancement products, some with ads claiming endorsements from Winfrey.
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 the Web site does contain the information, but 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.