TPG does request Telstra to do the porting, whatever that involves.
If you have confirmed that your landline phone is working via the NBN connection, you only have to cancel your phone service with Telstra, otherwise they continue charging you. (Seems like porting a number to another provider doesn't trigger any action with Telstra billing. This has been reported by other users.)
The procedure is, if you want to port your original phone number to TPG, you had to wait until the porting was completed, before cancelling the service. If you do it the other way around, your number might be allocated to someone else.
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