DEBT-IN and sharing details

Still getting call from these guys for a debt that is not mine or remotely has anything to do with me? I keep getting harassed by debt-in for a debt owed by a third party. Debt-in wants me to share the information of third parties for them to collects debts. Furthermore, FNB has been apparently sharing my details with DEBT-IN and DEBT-IN has informed me that I MUST share the details of said THIRD-PARTY under threat of harassment?