Is your offset account actually working?
An offset that was never linked looks completely normal. Same repayment, nothing odd on the statement. This shows what yours should be saving, so you can check it against what you are charged.
How to check it is really linked. Your interest should be charged on the loan balance minus your offset balance, every day. If your statement shows interest on the full loan balance, it is not offsetting. Ask your lender in writing for the date the account was linked to the loan, and for the daily interest calculation.
Offset checker by UnitMojo