First of all, if you are sure you aren't listed on the card as an authorized user or that you did not sign the credit card application, you can demand that proof of your liability be sent to you. Insist that valid documented proof be sent to you. Even if you are sent proof, make sure any signatures are yours and that your name was not forged. If forged, contact the securty department of the credit card company and file a written dispute.
Do not send any money, regardless of reason, to anyone, related to this debt, as that can be interputed as acknowledging liability for the debt.'
Get the address for the credit card issuer and send a letter disputing you obligation. Have a credit report sent to you to see if this debt is listed, and if so, send a dispute letter to all three credit reporting agencies. State that this is not your debt, you did not request this card, and that you are not liable for these debts.
The credit reporting agencies have 30 days from receipt of you letter to send the dispute to the credit card company, and they have 30 days to reply, and the agency has another 30 days to reply to you. So, expect 90-120 days before you receive anything back. You may however, see the item removed from the credit report during the dispute, but it may reappear later.
Disputing this with the credit reporting agency is the most important part. The collection agency does not care what you say. Until, they are told by their client that the debt is invalid, or recalled, they will pursue it.
The statue of limitations: Open account: 3 years, NOTE: Each payment renews the SoL on all items purchased within the 3 years prior that payment. If no payment is made, the SoL runs from date of each individual charge. Contracts: From date of breach or default, unless waived or performance under the contract is continued.
If it has been 3 years then there is no legal recourse for the agency, but they can still try to collect. It is up to you to know that you can not be sued for the debt, but it can still be reported on your credit report.
If you were not liable for this debt, then clean up your credit report and don't worry about the collection agency.