Welcome to the community!
I suggest to check the installation date that was sent to the e-mail address associatd with the account and in the event that you wish to keep the home phone number from Telstra, I highly recommend to keep the Telstra service active until the porting of the phone number is done.
Once the porting and the installation is completed you may contact Telstra directly for the cancellation of the service.
Let me know should you require further assistance.
I got a modem from TPG, my internet still running with Telstra NBN. Do I need to cancel my existing service before arrange TPG technician come to install it.