It will be great if there is someone who will constantly remind you that you are too engaged on your smartphone all the time. Ideally the person should be with you most of the time (e.g. your spouse, close friends or family).

Next, make some rules for yourself to follow. For example, no using phones during meals and after 10pm. Have some self imposed punishments whenever you violate those rules.

Finally, it will be nice to also have a distraction. For example, reading books or working out. During these times, chuck your phone aside and focus on the other activities.

Ultimately, getting rid of an "addiction" always requires self discipline. And it will be impossible without self discipline and the conviction to break the addiction.

P.s. this answer is posted from a smartphone. Lol..