My income has doubled and child support australia doesn’t care.

Last year I earned 74k, just did my tax and CSA have updated my income accordingly, however I have just started a new job where I will be earning 150k + this financial year, I called CSA and they won’t accept my estimate because it isn’t 15% lower than last year. They said it will be re-assessed next year when I do my tax. They also assured me that I won’t end up with a giant bill. Can somebody please tell me what’s going on? It sounds absurd that I’m going to be paying child support at a much lower rate than I should be with out any consequences.