Amex Debt Collection Complaint

Amex Debt collection department,

Credit card Cont'd attempts collect debt not owed Debt is not mine Colorado

I left my job and had a corporate American Express card. I turned the card in when I left, but after that a bill came in for equipment that the company purchased. The company should have paid the bill but did not, possibly because the only notice given was to my company email address which no longer existed, and no paper bill was sent because the company had requested paperless transactions. I received no notice until 3 months later by mail, by which time there were late fees conveniently greater than the original bill. Now AME- calls me every night, but I keep telling them the bill does not belong to me but to the company. They are threatening to cancel my personal account and attack my credit rating if I do n't pay this bill immediately, even though it does n't belong to me.