Configurations providing a reusable context model for a user interface over SMS for interacting with different levels of a user interface (UI) within an interactive system are described. An SMS server can implement the reusable context model in which an available number from a sequence of numbers (e.g., a block of numbers) is assigned to a first level of the UI. The first level of the UI can include a set of options corresponding to different operations within the interactive system. When an SMS message, which includes a selected option from the set of options from the first level of the UI, is received over the assigned number, the SMS server can determine whether to assign an additional number from the sequence of phone numbers for responding to the received SMS message. The additional assigned number can correspond with a second level of the UI within the interactive system.