The phone rings twice, then done..... When you return the call, they need to speak with a named person...when asked, they provide no information, other than to keep asking for the name... Sounds in the background are a vast array of other callers on phones. when you show any reluctance, they hang up. This is usually the M.O.  of Collectors..
I have noticed they use 3-4 different phone numbers starting 78

Keep calling and harassing after have been notified it was a wrong number then when I call back to get information about the company so I can report it they hang up.

I don't answer calls that are from area codes I don't know. Called 3 times this afternoon in about 3 to 4 hours, on my cell.

its a collection company...that calls...doesn't say anything for 15 seconds, then you hear a beep, then silence again, then elevator music for over a minute to have someone with a very thick accent ask "Can I help You"