My Trello account (@nachogg1) was created in May 2016 and I've been using it ever since:

A few months ago I updated the password and lost it soon after. However, my Smartphone still had access.

I tried to change the password using my e-mail, which was recognised as valid, but Trello created a new account instead (@nachogg2).

I am sure it was the original e-mail the one that I wrote, because I still have the May 2016 welcome e-mail saved in my inbox. I tried recovering my account using my Smartphone, given that I have full access only through the Android app, but reading some sources I realised that security changes are only allowed through the website.
I wish there is a way to recover my account, or at least, send all its cards to my unexpected new account.