@Jacobk I do see our support team attempted to reply to the messages you submitted through our help page. This being said, it looks like all of their messages failed to send due to the email address you provided being invalid.
I'm happy to try and assist on my end.
I do see your account is currently upgraded to Pandora Plus through Apple at the $4.99 (plus tax) monthly rate.
To clarify, does that error pop up when you attempt to upgrade to Pandora Premium at the $12.99 (plus tax) monthly rate?
Let me know.