The same thing happened to me. When I did pick up, it said one of my cards had been disconnected and if I wanted to reactivate it, to type in my 16 number code. But! I didn't catch which card and more importantly, that didn't seem likely that a machine would be handling it, not a real person.
They called continuously for days and said nothing when I picked up. Finally I got a young woman asking for someone else. I said they had the wrong number, and then she asked if I was a homeowner looking to refinance and I said NO! And she said uhhhh ok and hung up. Terrible telemarketing tactic!
Whenever they call and I am home, I just pick up the phone and immediately disconnect. Other times on my caller ID they NEVER leave a message. Today after they called and I hung up, I called them back from my unlisted, caller blocked phone number. The message I got was please call back and unblock your number if you want us to stop these calls. One has to wonder why they don't even identify themselves. It was near the end of May that I finally....after all these years put my number on the Do Not Call list. So, hopefully, after July 1, if they continue I will lodge a formal complaint. If they were really calling about something important, they would leave a message. Caller ID is the best thing invented for pest control. Better than Terminix.