The terminal is only for the technical processing of the card payment. All communication takes place via the app on the smartphone. Depending on which user you log in with, the payment is transferred to the account of user X or to the account of user Y. The payment is then transferred to the account of the other user. You can also make one mobile phone per account (WLAN connection is sufficient) and use only one terminal that the various mobile phones access, if changing users is too inconvenient for you.