Don't get between a teenage girl and her phone.
I've grounded my girls from their phone and all social interaction (computers, house phone, visitors, etc.) You'd think I was giving them the "death sentence".
I just remind them that they wouldn't have any of this crap if I wasn't paying for it. End of argument. Keep arguing, and I'll increase your time out.
One of the things that we have figured out, is that the program I use for monitoring my WiFi network actually shuts down their laptops' WiFi cards. If I turn them off, they can't connect to anything until I turn them back on.
I do that periodically when they are sucking up the bandwidth and I can't connect to WF.