Take the children out to play.
When a child wants a mobile phone, you can take her out to play games and so on.
Cultivate children's hobbies
Cultivate children's other hobbies. For example, she can draw, dance, play the piano, learn calligraphy and so on.
Explain the disadvantages of playing mobile phones.
Explain the disadvantages of playing mobile phones to children. Older children can reason with their children and talk about the dangers of playing mobile phones.