Did you know there was a time before people had cell phones? It might seem impossible to fast from your cell phone, but you might discover you have more time to pay attention to other people and to the Lord.
If you cannot completely fast from your cell phone, then strictly limit the time when you will use it. For example, if you need to call mom or dad to let them know when you are ready to be picked up, then only use it for that.
Or make it off limits when you are at home. Spend more time talking to your family.
Think about your cell phone use and cut it off as much as you can. Offer it as a Lenten sacrifice.