You already have a Split Pay account tied to that phone number, and the screen is pointing you to it. It shows the email on your main account — sign in with that email and everything is there: your eligibility, your payment account numbers, your history.
Every customer has one main Split Pay account. If you enter a new email with a phone number that matches your existing account, we'll always point you back to your main account's email instead of creating a duplicate — a second account isn't possible.
If you don't remember which sign-in method you used originally:
Check your inbox for the welcome email from Split Pay — it'll indicate which method
Apple users: your account email may be a private relay address that looks like
xxxxx@privaterelay.appleid.com
If you can't access the email shown on the screen, see I lost access to the email on my Split Pay account — what can I do? — there's more we can do than you might think.