Hello @Yany
Have a good look at your bill and see if it was "estimated", I have a feeling you received an estimated bill.
AGL your "Retailer" are not the ones that send out a meter reader.
This is done by your Energy Distributor "energy supplier" if they do not supply AGL with a meter read.
Then AGL is forced to do an estimate based on your past usage and this is not an easy thing to do as it gets colder power usage changes etc.
Then when AGL get a meter read sent to them by your energy distributor your next bill is adjusted to reflect this.
Generally speaking if you do not have a smart meter you are at the mercy of your Energy Distributor sending out a meter reader.
If it were me I would pay my bill then get it sorted out.
I do not work for AGL, I am only trying to give you some insight as to why this may have happened.
Regards
John