Not auto changing currency on only category pages

It always shows the default currency (british pounds) on category pages but then the correct currency (in my case AUD as viewing from Australia) when on individual product pages. Sometimes after adding products to the cart it will correct for one category page but still show the wrong currency on other category pages. I’ve tried changing all the settings and turned of caching but nothing worked and sales have gone down over the last few days trying to fix the issue