I do not understand why your monthly bills cannot be issued from the 1st of the month to the last day of the month.
I was with Momentum Energy for quite a while, and they issued their bills monthly.
It means that your bill data lines up with the data from the online portal of the wholesaler, plus it also lines up with the solar panel data that is provided monthly.
I have found it very difficult to understand why this is the way your bills are issued, when the wholesaler provides the information to you "monthly". I think this is the first thing that needs to be fixed.