I wonder if anyone else is experiencing what i am. I have had a contract for my phone for almost 2 years. It ends in February. I find it frustrating and unacceptable that for the last few months, having declined offers to change my plan, that i have started to receive optus usage bills $50 and $60 more than the $100 monthly amount! Coincidence? I doubt it. I have also noticed that my usage is noticeable faster these last couple of months. I am not happy at all. Will be making some changes to my provider very soon. Tired of this nonsense.
So your theory is that while solidly under contract Optus has billed you correctly but just as your contract is coming to a close and you will have the freedom to choose any provider, Optus have decided to make a last desperate grab for a few extra $ thereby almost guaranteeing you will leave? Interesting.
Have you tried to confirm what is using the data (either via Optus app or looking at the usage settings on your phone?)
Would be nice to know how much data you get. The internet is getting to be a bigger waste of data every year. I don't know if you are using it for Facebook or what.
You may even be getting billed by the usual premium SMS scammers.