A method comprising: at an electronic device in communication with a display and one or more input devices, wherein the electronic device is enabled to perform the steps of: receiving, via the one or more input devices, an input to display a user interface for initiating a messaging conversation with a respective contact; and in response to the input, displaying the user interface for initiating the messaging conversation with the respective contact, wherein: in accordance with a determination that the messaging conversation is a new messaging conversation with the respective contact, the user interface includes a visual indication of a first respective cellular identifier to be used for the messaging conversation, and in accordance with a determination that the messaging conversation is not a new messaging conversation with the respective contact, the user interface does not include the visual indication of the first respective cellular identifier; while displaying the user interface for initiating the messaging conversation with the respective contact, receiving a respective input; and in response to receiving the respective input: in accordance with a determination that the respective input is an input selecting the visual indication of the first respective cellular identifier, initiating a process to select a second respective cellular identifier, different than the first respective cellular identifier, to use for the messaging conversation; and in accordance with a determination that the respective input is an input to initiate the messaging conversation, initiating the messaging conversation using the first respective cellular identifier. receiving, via the one or more input devices, an input to display a user interface for initiating a messaging conversation with a respective contact; and in response to the input, displaying the user interface for initiating the messaging conversation with the respective contact, wherein: in accordance with a determination that the messaging conversation is a new messaging conversation with the respective contact, the user interface includes a visual indication of a first respective cellular identifier to be used for the messaging conversation, and in accordance with a determination that the messaging conversation is not a new messaging conversation with the respective contact, the user interface does not include the visual indication of the first respective cellular identifier; in accordance with a determination that the messaging conversation is a new messaging conversation with the respective contact, the user interface includes a visual indication of a first respective cellular identifier to be used for the messaging conversation, and in accordance with a determination that the messaging conversation is not a new messaging conversation with the respective contact, the user interface does not include the visual indication of the first respective cellular identifier; while displaying the user interface for initiating the messaging conversation with the respective contact, receiving a respective input; and in response to receiving the respective input: in accordance with a determination that the respective input is an input selecting the visual indication of the first respective cellular identifier, initiating a process to select a second respective cellular identifier, different than the first respective cellular identifier, to use for the messaging conversation; and in accordance with a determination that the respective input is an input to initiate the messaging conversation, initiating the messaging conversation using the first respective cellular identifier. in accordance with a determination that the respective input is an input selecting the visual indication of the first respective cellular identifier, initiating a process to select a second respective cellular identifier, different than the first respective cellular identifier, to use for the messaging conversation; and in accordance with a determination that the respective input is an input to initiate the messaging conversation, initiating the messaging conversation using the first respective cellular identifier.