Hey there,
I'm so sorry to hear you're having trouble with your Apex Coins purchase. I can't action your case with the support team but I want to help you get it sorted out as smoothly as possible so there are some things I'd recommend trying before you update your support case.
First things first, let's make sure you're logged into the right EA account that's linked to your Steam account. You can double-check this by heading over to your EA Account Settings and looking under the "Connections" tab. Take a look at the Steam section...