JB HiFi are discounting the S21 and S21 Ultra by $1,100 when a new customer ports onto Telstra's $99/month plan. I bought this last Friday and was told the offer runs until June 27th.
I didn't take any pictures of the in-store signage, but I have attached my receipt where you can see the $1,100 discount is put through as a gift card.
Here's a quick search for the S21 range if you want to check for local stock.
If you're after the S-Pen for the Ultra, they also have 30% off cases, including cases which come with an S-Pen included:
$69.30
$90.30
Can I cancel the plan immediately? I remember there was a way to do that with these Telstra plans