Evidence that embattled bank Wells Fargo had swindled some of its clients emerged in a June conference call led by its managers, according to two employees who were present during the call, The Wall Street Journal reported Monday.

The revelation, based on an internal assessment, reportedly came following years of rumors within the bank. Of the approximately 300 fee agreements for foreign exchange trades reviewed internally by Wells Fargo, only about 35 firms were billed the price they had been quoted, the employees told the Journal.

Wells Fargo charged one of the highest trading fees — at least two to eight times higher than industry standards, according to the bank's employees and others in the sector, the Journal reported.

The latest case shares important similarities to Wells Fargo's ongoing sales scandal: Under a highly unusual policy, employees' bonuses were tied to how much revenue they brought in, the report said.

The practice reportedly led retail employees to open as many as 3.5 million fake accounts, in a controversy first brought to light last year.

Read more on the Wells Fargo currency trades controversy in The Wall Street Journal.