They just did the same thing to me, and it has to be a telemarketing call, it is against the law to call back to back like that. It's called harassement, in the United States.
I'm not sure if it was a debt collector calling. I didn't answer because I didn't recognize the number. After their call was eventually sent to voicemail, they called again about a half second later. No voice message. Only problem I have with this is my cell phone is my work company's property. It's not listed in my name.
I received a call from this number on my cell phone, they said nothing on my voicemail, but it sounded like panhandlers from the Taj Mahal in the background.
They just did the same thing to me, and it has to be a telemarketing call, it is against the law to call back to back like that. It's called harassement, in the United States.
The guy sounds like from India or Pakistan says my first name and asked whether I pay the medical bill for Sheila or something like that. (accent is pretty much confusing). Since I do not know who is that guy, I said "no" and he dropped the phone.