Calm down, take a deep breath...I know this is what I needed to do when I recieved the EXACT same type of phone calls both at home and at work, non-stop and at the time I had no payday loans or had taken any out in the past so I knew these calls to be bogus from the start.
The calls started coming in around last summer, and each time it was from a person with a heavy indian accent claiming to be from a lawfirm and some payday loan company wanted their money back and demanded I pay him immediately.
I was first really unnerved by these calls, and startled, I didn't know what to do as I'd never recieved collection calls before, however I gathered up my wits and really sat down and thought it over, even contacted a lawyer which confirmed them to be bogus call and told me how to handle them.
When I recieved yet another call from a person claiming to be from a law firm I asked first his name, in which he acted confused, and rattled off something so fast I couldn't write it down, I asked him to spell it in which he did, I then asked where he was calling from and he hung up, I fired back by calling straight back only a different person answered and I demanded their name and the name of their company and told them I wanted the information so I could turn it over to my lawyer, the person actually BEGGED me to forget about them and told me they took my name off the list, I laughed so hard. I haven't heard from them since. So my advice is challenge them, make them give you information about who they are, act like your out to investigate them, make them nervous, as you don't owe them a single dime and you can prove it!