: Open the Messages app; a prompt to "Use Messages via Satellite" will appear automatically if you have no signal.
Depending on whether you're trying to fix a reception issue or send a text with no signal, you can manage your iPhone's reception and messaging through the following methods: Checking Precise Signal Strength iphone reception
This opens a hidden menu showing your signal strength in (decibel-milliwatts). A number closer to zero (e.g., -50 dBm) indicates excellent reception, while -110 dBm or lower indicates very poor signal. Texting with No Reception (Satellite) : Open the Messages app; a prompt to
: Works automatically over Wi-Fi for Apple-to-Apple conversations. : Open the Messages app