Q: I am trying to purchase credits online but I'm getting an error message that I need to insert a postcode?

A: Just hover over the My Account drop-down menu, click on Account Details.

Then you need to click on the pencil icon in order to add in or edit your details. 

Once you've clicked on the pencil icon, you will see a text box for you to enter your postal address details in, including a postcode. Save those details by clicking on the tick, and you should now be fine to proceed with your purchase.