Paypal repeatedly calls me from an unlisted number sometimes XXXX times a day. Sometimes XXXX to XXXX minutes after the XXXX call. I answered the call once to see who it was. It always comes up as " Unknown '' on my phone so I generally refuse the call from such numbers. 
They said they were collecting a debt from PayPal, which I do owe. I said I know about the debt and that I would try to get a payment said thank you and goodbye. 
They still call me repeatedly, the only way I know it 's still them is the voicemail they 've left maybe XXXX times. Most times it 's just repeated phone calls from " Unknown ".