**How can I tell my date to not use her phone unnecessarily during dinner?**

I have news for you. **You don't get to control your date's behaviour.** Unless you are their parent or their boss.

You can however do two things:

 1. Communicate to your date how you feel when she uses her phone unnecessarily. 
 2. **Ask** if she would mind not using her phone. It's her choice to respond or not. And make sure you ask nicely, and that you make it clear they have the option.

It may seem like a small thing but it isn't. People do not like being told what to do. And the fact that you phrased this as "tell my date to..." several times in your question makes we wonder if you have really grasped the point that you can't control people's behaviour. As an exercise consider how you would feel if you were **told** by a date not to do something that you normally did and liked doing.