Put another notch in Uber's bad public relations belt.

The car service app was given an F rating from the Better Business Bureau, the consumer advocacy group announced on Thursday. Over 100 complaints about the company's surge-pricing strategy, and other issues, lead to the bad review.

"Some consumers claim that they were told the final cost of the transportation service the company provided (through Uber Technologies' phone app, the driver, and the consumer's receipt), only to be subsequently charged a substantially larger amount," the Better Business Bureau said.

Uber's surge-pricing has been the subject of much criticism in the past. During busy hours, like during a rain storm or on New Year's Eve, riders are charged at a higher rate. The company says the move helps customers by making more cars available.

"With surge pricing, Uber rates increase to get more cars on the road and ensure reliability during the busiest times," Uber's website explains. "When enough cars are on the road, prices go back down to normal levels."

Of course, Uber is far from the first company to engage in surge-pricing. Airline companies and hotels are known for jacking up prices during holidays and other busy travel times. But Uber riders complain that they're not adequately informed of how high their trip's cost will be. In the early months of the company, customers were livid after being charged hundreds of dollars for rides on New Year's Eve. In some cases, users claimed they weren't notified about surge pricing until after the trip.

Uber's rivalry with Lyft, another on-demand car service app, has also been a major controversy. In August, Lyft claimed that Uber employees were requesting rides and then immediately canceling them to try and turn drivers away from the service. Uber denied the allegations and accused Lyft of the same practice.

Lyft was also given an F rating from the Better Business Bureau, but received far fewer complaints.

As the New York Times pointed out, this is the lowest possible grade a business can receive. The highest is an A+.