I can’t use internet on my iPhone - [Could not activate cellular data network]

Everytime I bring up ‘Mail’ or ‘Maps’ or anything really, I am greeted with this message:

Could not activate cellular data network

And then, predictably, nothing happens and nothing works. Meanwhile, I can still take calls/texts. This has never happened before. [I have tried using Airplane mode as well as shutting down and restarting the device - to no avail] Does anyone know what’s going on and how I can fix this?

[UPDATE: - oh thank god it’s back on. Thanks guys, I guess it just wanted a break.]