Metra promised customers Tuesday it would make good on double-charges that occurred on credit transactions last week.
About 1,500 customers were affected by the mistake June 27 that occurred at area station ticket windows.
As of Tuesday, all double charges were expected to be reversed and posted to customers' credit card accounts within two to three days or by Saturday at the latest.
Metra officials apologized for the error and said they would work with the credit card processor to see how the problems happened and set up protocols to prevent further glitches.
The agency started allowing credit card sales at stations in February 2010 after pressure from lawmakers. Up until then it had been cash or check although Metra began selling ride passes on its website using credit cards in fall 2009.