It would depend on your phone, mine is really silly I have to add them as a contact then in my contact settings block them. In case you were wondering I have Huawei phone.

I called back number (03) 8393 0721 just kept on ringing and then an option to leave a voice mail but it didn't say what company.

You missed a call from (03) 8393 0721, who did not leave a message. This message was provided by Telstra at no charge to you.

This number calling everyday am and pm getting sick of it...how do I block ?.