Advantage Financial Services is calling my job and threatening me

I’ve been dealing with Advantage Financial Services for a few weeks now over an old debt I’m honestly not even sure is mine. At first it was just multiple calls a day, but now they’ve started calling my workplace after I specifically told them to stop. They also left a voicemail saying they’d “escalate legal action” and mentioned wage garnishment like it was already a done deal.

I’m stressed, embarrassed, and not sure what my rights are. I thought debt collectors couldn’t threaten things they can’t actually do or call my job after I asked them not to. Has anyone else dealt with Advantage Financial Services like this?

I found this site that breaks down the harassment signs and what to do:

Stop Advantage Financial Services Harassment

Just trying to figure out my next step. Any advice would help.