Female said name was Alex calling about my hot water system. When advised it was an apartment block,then asked who internet was with. Asked where she got my number as I am on do not call register she said let me check and hung up. When I tried calling back (to see where they were calling from) said number was not connected.

Called twice…ending 9820, 9824…feels like a scam call as no message left.

My phone identifies suspected scammers and fraudsters. I've blocked this number.
After recent events of hackers cracking the governments cyber-security, telcos being hacked and in the past few days one of the bigger e-stores have had their customer details compromised.
I was careful with suspect numbers before but now I'm 100% more vigilant.
So you useless time wasters, go get a real job and stop annoying hard working people who are busting a boiler to get food on the table to feed their families.

Just before 1pm. No message was left.

Rang back, busy tone. The second call back , the number is not connected.