They never stop ringing and never leave a message. Everytime I block their number they ring from another extension. The first four numbers are always the same.

Telemarketing company for a energy company that just won't stop calling from multiple numbers. Blocked!

At first I thought this was some sort of canvasser but it turned out to be ActewAGL who is my own electricity provider.

Called it back and received a message offering to help find a better deal on electricity and gas costs.