If you shopped at Macy's before Christmas, you may want to double check your debit card. The retailer says a glitch in its system caused some card to be billed twice on Dec. 20. It happened specifically between 1:00 and 2:45 p.m. In case you're wondering, it happened the Saturday before Christmas, which is typically the busiest shopping day of the holiday season. Macy's says it's taking steps to correct the errors and will remburse any customers who had overdraft fees because of the problem.