Hi @markthomo25, That sounds unusual. If your plan's monthly fee is $69.99, that's what TPG should charge you.
I'm assuming you might be on NBN (because TPG doesn't have any $79.99 ASL2+ plans)? If so, there are only 2 $79.99 plans I can see at https://www.tpg.com.au/nbn - are you on either of these?
I'd recommend confirming the plan you're on at https://www.tpg.com.au/account (log in and then click on "Plan and Contract Details"). If this isn't right, definitely get TPG to fix it for you.