What's the problem you're having linkiepoo?
This doesn't work on my Galaxy S2, I had the old app (My Account) installed a while ago but since about 2 weeks ago it won't let me access this app. It keeps on telling me that my phone isn't supported (We're Sorry! This feature isn't available for your service. For more information please visit our website)
Sounds strange - that model is definitely supported.
Have you tried uninstalling and reinstalling the app? Is there only one version that you can see when searching My Optus?