Hi there @theconstantgardener, sorry to hear you're having issues with this.
Can you clarify what plan you're on at the moment as shown in your plan tab?
Do you happen to have another email address that you used for Dropbox in the past perhaps?
Also, where did you upgrade in the first place? Was it through the website directly or via the app store on a mobile device?
Let us know what you find and we'll take it from there.