Dear Creditnet: I'm currently receiving collection notices from American Express for an unpaid balance on an old corporate credit card. I left the company where I had this card in late 2011. I have combed through all my Amex bills, corporate expense reports and reimbursements, but I've been unable to find any unpaid charges on the card. In addition, because the card was in my name and I incurred all the charges, my former employer takes no responsibility for the unpaid balance even though the charges were made solely for work purposes. Will this affect my personal credit? What should I do now?