Configurations providing a rolling sequence model for a user interface over SMS for an interactive system are described. An SMS server can implement the rolling sequence model in which a number from a sequence of numbers (e.g., a block of numbers) is assigned to a user session. A subsequent number from the sequence of numbers is assigned for each session turn-around. Upon receipt of an SMS message from a user to initiate a session, the SMS server assigns a first number from the sequence of numbers to a user session. The SMS server then assigns the next phone number to the user session after receiving a subsequent SMS message from the user. In the event that the last number from the sequence of numbers is assigned, the SMS can cycle through the sequence of numbers by assigning the first number to the user session.