This is a SCAM
Do not follow their orders.
They claim to be from Telstra and say that you are having problems with your internet connection. They ask you to download a program so they can take control of your computer. Their goal is to steal all of your personal information, including your internet banking passwords.
I have recieved phone calls like this before.

Have rung twice so far on Good Friday, no message left.

Have rung a few times on different extension numbers. 5245 and 5222
Have not left messages

Just another scamming call centre. They seem to have a whole bundle of numbers in the Rockhampton area. Probably bogus, but what telco is allowing them to patch into the network and fake a number?

Sounds like a call centre in the background but they don't respond when say hello. Now letting these call go to message bank, but they don't leave a message.

pair of Indian claim that from Telstra

Claim to be from telstra and internet services not working