I want to post a quick update on the issue. Guess what? I was wrong to think that Bubble would not be able to reverse my app plan to legacy again. Well, they accepted their fault without any argument at all.
There was something wrong in their billing workflow which caused this issue. It doesn’t happen often; my case was just an exception, and they jumped straight into looking into and fixing this issue.
Not only did they respond to this issue wholeheartedly, but they also switched my app back to the legacy plan.
Big Hug to the Bubble Team <3