SHANGHAI, Jan. 29 (Xinhua) -- Complaints over bike-sharing services went up by more than 40 times in 2017, according to a report by Shanghai Consumer Council.

The council received 7,978 complaints about bike-sharing services last year, according to the council. Xqchuxing, Mobike and OFO were the top three companies facing the complaints.

Customers in Shanghai were upset by delays in the return of deposits, abnormal charges and poor customer service.

In some cases, costumers did not receive their deposits two or three months after request, while many bike-sharing companies promised refunds within seven days. In other cases, bike-sharing companies wrongfully charged users due to various systematic problems.

"Bike-sharing companies need to focus more on providing high-quality services and stable systems," said Ning Hai, deputy secretary general of the council.

More than 20 million shared bikes are now on the streets of Chinese cities, according to a report by the China Academy of Transportation Sciences.