Reliant Recoveries Inc Calling cell phone repeatedly for wrong person Everett, Washington

I first began receiving calls on my cell about a month ago. I did call back the # on the caller ID as my husband suggested only to hear that it was Reliant Recoveries & they were closed. The very next day, I received 2 phone calls, one with a voicemail from "Leon" looking for a person I've never heard of (possibly the former cell phone # owner). I did not return any calls after looking up this company on the web--what a terrible reputation they have--I did not feel at all comfortable calling them back to tell them they weren't looking for me. The following weekend, the phone rang while I was in line at the store--I opened the phone to see who was calling & it was their #. I hung up the phone & of course it rang again before I got to the car--this time a rude voicemail from "Leon" again, addressing the debtor by name and "since you hung up on me, we will be looking for the full amount you owe us." They waited a few days again, called on Monday, then 2 weeks later (a Saturday again) 2 calls showed up within 20 min. I'll wait them out a bit until a stop communication letter with only the cell phone # listed on it (they have no way of knowing my name or address) will be sent. As someone suggested , I saved their # into my phonebook & turned the ringer on the phone off for their calls. I am also writing down all info.