If your handset is tied to a network then there can be a delay in them rolling out updates as they 'tweak' them. Mine was direct from Samsung and I was also on Beta testing for A12. You can't force the update without going into flashing the software etc (and invalidating warranty). The update is packaged with the Feb Security Patch so hopefully you'll get it soon - just keep checking via Software update in settings.
my phone was second hand but it had a load of EE networks apps on. I don't use EE as I enjoy paying a reasonable amount per month for my phone. It's not locked (I'm on 3) but I'm to believe it runs EE firmware
You're in the hands of waiting for EE to publish the update to your current version via Samsungs' OTA system. It's a matter of sitting tight. If you wanted to move away from EE firmware then generic firmware files are available - but I am neither promoting this nor advising this.