Splitwise says my phone number "has already been taken" when I try to add my phone number to my account
To access the Splitwise account with that phone number, just go to our password reset page and enter your phone number. You'll receive a text message with a link to reset that account's password and log in. Once you log in to that account, you can either merge it with your existing account, or you can simply remove the phone number from the account settings page (which will allow you to add that phone number to your other account).