this number has incoming call restrictions message when called back.

Same thing, a few seconds silence then "Goodbye"!

Scam caller spoke with foreign accent; block it

When answering machine picks up the call they hang up

Some sort of call centre ( can hear people in background before they hung up without speaking). Very surprised that they called a mobile number! Very few people have my mobile number so they could be just stepping through all mobile numbers.

Missed the call. Dial back and get ‘incoming call restrictions’. Likely spam.

They keep ringing but don't leave a message. I'm certainly not going to waste time, money and security by calling them back!

Silence for 5 seconds then voice says "Goodbye"

This number has incoming call restrictions.