Users in Australia seeing prices on SGP, why???

I have set few currencies in my store. Which should auto detect by user location.

However, I had three users today accessing from Melbourne, Australia and they currencies were Singapore (SGP). Which is totally not the case.

It is not the first time that happens actually.

Can someone please help me fix that once for all?

Note: Please don’t come and say “we checked your website and is working normal, because that’s not the case” I am using Heatmaps and I can see everything that the user do on my website, and the same issue happened three times only today.

Thanks!