Issue with incorrect currency showing

On the weekend, I went to buy a Sims 4 kit and the amount was shown in English pounds.  I live in Australia, and my EA account and my computer both show that information.  Today, I checked it out and it shows the correct amount on the initial page for the kit but when I press 'purchase', it shows the amount in pounds.  What can I do to correct this because I won't buy anything while it's incorrect?