Accounts won’t merge


I have a new phone and new phone number. I entered in the new phone number when I installed sweatcoins. The app did not ask me for my email address. I tried changing it in the profile section to the email matching my odd account; however the app stated over and over this email is already taken.

How can I merge my accounts then? AND my new phone number is linked to an account belonging to someone by the name of Jack?