When I answered they hung up. i think that is to see if you answer then they put you on another list for the telemarketers to call you. ive stopped answering unless it a known number

When I answered they hung up. When I tried to call I got a "not in service" message too

Just received a call from this number for the first time I answered even though I was at work they hung-up very annoying block this number.

Called cand were trying to sell something. Obviously working off script as when I interupted they had to go back to beginning.
Asked where they got my number from and replied "from electronic white pages". This is an outright lie as my number is not listed anywhere.
When I tried to call back on both landline and mobile is got a "not in service" recording