We have an existing ADSL connection with another ISP, and a telstra phone, for which we are paying the monthly line rental.
If I move to the Optus ADSL2+ service, with the included phone line, can I stop paying the Telstra monthly line rental, or do I need to keep paying the Telstra fee in order to retain the ADSL2+ service?
There is a chance that you could lose the line totally, if you attempt to move to Optus, because NBN sucks them all up. Be wary of that.
You can transfer the whole lot to Optus. Just be aware that you get what you pay for.
Providing you don't have an outstanding contract with Telstra when you port your home number over to Optus this will cancel the account with Telstra.
Still worth giving Telstra a ring once the transfer is completed to confirm the account is closed.