A debt collector (asset care) started calling me to get to my sister.

She lives in a different state

They never said they were debt collectors on the phone, just the company name (which a quick search told me enough) and that it was a private "business matter" which in my past life of a debtor screams debt collection.

I know that calling family members to get to another is pretty much illegal, but is it also illegal to tell me it's a "private business matter" when it's obviously debt collection?

Should I go ahead and send them letters detailing what they did to ask them to stop?

File a complaint with the feds?

Any help is appreciated l, thank you.