Postal delivery company Yuantong Express could face falling customer numbers after media reports that personal information on the company's express envelopes is being peddled on the Internet.

"We're concerned about the security of our personal information after the scandal with the company, so we're considering changing to another express courier," said Wang Yan, who works in the administration department of Xizi Otis Elevators, a customer of Yuantong since 2009.

Several companies have already reported switching from Yuantong, including Shanghai Jinxing, which is based in the Pudong New Area and whose main business is the import and export of wood products.