Hi sabresong,
Credit Recovery System, Inc is a Collection Agency in Houston. Perhaps they are trying to contact you to collect some debts that you owe. However, they are bound to inform you that they are responsible for the collection of the said debt and they should produce written validation in support of their demand. If they cannot, you need not pay a single penny.
According to fair debt collection practices act, collection agencies cannot contact your friend, except to inquire about your contact details. But they can contact your co-signer any time.
If you find them violating fdcpa rules you can file complaints against them with BBB, DA's Office or FTC also.
What you can do now, ask your friend to refer you if they call him in future. You can make some arrangements to repay the debts if their demand is legitimate. You can always ask for a debt validation and they should send you all the details of the said debt in writing.
Try a search with BBB to know more about Credit Recovery System, Inc.
For any more help, please ask your queries in the forums.
Regards,
Bryan