Re: Extra charge $10, for 1gb for exceeding monthly usage fee.
Fair comment. Unfortunately Optus expressly state otherwise (I actually suspect their systems aren't capable of auto adding in whatever portion is left of the 1Gb. )
The fee is unreasonable on many levels. On the last day of your month, at 11.59 and 55 seconds Optus will (with a straight face) happily top customers up for 5 seconds, add $10 to their bill before wiping the at data at midnight.