Potential scam caller. Answered and number hung up without anyone saying anything

Caller: Calls and hangs up if answered

This is a scam call/robo call. They call to verify if a line is active. Once answered they hang up. It seems the more you answer the more they call.

As above potential scammer, answered call, then they hung up, rang number back, funny that number is not in service.

scam

Scammers

Caller: Unknown

Calls multiple times a day under at least 5 different phone endings eg 871, 872, 875, 877
Hangs up immediately however when i call back they stat asking about if i need to take out finances