Account Invoicing Issue + Pro Upgrade

Hi gang, I have two Cloudflare websites I'm wanting to upgrade to the pro plan, however there is an outstanding invoice I can't decifer as to what it's actually for - it references a previous invoice that states it's fully paid.
I've submitted a support case #01442091 however this was submitted 25/3/2025 and no response yet.
Any help would be appreciated, cheers