I don't answer calls from numbers I don't recognize. They called, I didn't answer. They didn't leave a voicemail. I called the number back, using '*67' to block my Caller ID. It's Portfolio Recovery Service.
These jerks keep calling constantly trying to collect a loan over 30 years old, never mind that the family member who had the loan has been dead that long also I gave them the number for the cemetery and told them to try there. And they still keep calling, I have 42 numbers blocked from them, so good luck.