If you’re being asked for your phone number, it isn’t the same email address;
**If you already have an account with Monzo and you’re trying to login, and you are asked to enter your phone number, this always means you have entered the wrong email address. Always. The phone number prompt only ever occurs on the sign-up flow, when entering an email not already tied to an account, not the log-in flow when the email already exists for an account.