With wifi for calling and data there really is no way to block the phone
unless you take it away.
Family Allowances does minimal control over a line (search the threads - it's clunky, and doesn't control data).
If it's an extreme situation once or twice a year, you can do a temporary suspension. But, you're limited to two a year. (This was recently identified in another thread since that's how they were controlling).
Unfortunately, the only real answer is to take away their phone. You could combine replacing their smartphone with a dumbphone and Family Allowances (they don't get data on the dumbphone and you can turn on/off access to talk/text except with certain people -- and, this gets around the "my child uses their phone as an alarm clock" excuse).
The other option is as gramps28 said -- take the phone from the child. If they use their phone as an alarm clock, buy a cheap alarm clock from Walmart or Amazon and make them use that.
...and, as for the wifi comment gramps28 said... you can block their wifi if you have a router that supports it (Comcast has recently advertised shutting off devices to get the family to the dinner table). The problem with this is kids are generally smart and learn passwords. But, it can be effective if you maintain it properly.
But, yes. Taking the device away. Or, you can do as a friend of mine does -- take their charging away. Let them decide how long they want the battery to last. Is it worth it to text a friend or watch a video or send a snapchat when you don't know when you're going to get your charging cables back? (This doesn't particularly work if chargers are easily accessible everywhere in the house)