Legally speaking, you can make direct payments to the original creditor unless the debt is sold to outside collection agency. You need to call the creditor and verify the present status of the account. If they have your file, you can work out payment arrangements with them.
You also need to confirm if the CA calling you has your file with them. The debt is to be validated in writing mentioning the principal amount and the interest calculations. They should also send copies of the contract you signed with the original creditor.
The CA must send the information within five days after the first call. If you have not received anything yet, send a DV letter making your legal move.