I didn't answer because I didn't know number. After reading above, I don't owe anybody money. Well I do but I'm not behind on anything and never have been. No message left so probably a scam trying to get your card number then you will be in deep doodoo.
Smart move. Get all the information you need. No collection agency is that willing to help without threats. If they threaten you...make sure you have a cheap recording device you can get at Walmart or Radio Shack to record their threats. After the threats...tell them you just recorded everything they said on a device. They will hang up so fast you won't even know it.
If your home or cell phone has a reject number feature (Verizon does) or my home phone has a blocking feature....use it.
This message was from June 2015, That should tell you something. I did get a call from them today. Didn't answer, called it back...no ringing...nada. Block these a holes.