It is a much better idea to sit down and talk to them in a friendly and relaxed environment where they do not feel threatened or under pressure. Try to build a trusting relationship with your children where they can feel confident enough to approach you regarding important or personal issues, rather than hiding them and being secretive.
The majority of the time, children’s text messages are intensely private to them but will have little meaning to anyone else, so it is best not to invade their private lives by intruding on personal messages.
Do not ask them directly about what they say in their text messages or while they are on the phone as they are likely to close up and not offer any information. Ask them questions about their lives and show a genuine interest in their friends. Many teenagers will be reluctant to talk about personal issues or their friendship but if you show an interest without being overly pushy, they are bound to tell you snippets of information that should give you the information you need. If your child seems upset or sad, or even the opposite and is excitable and happy, these are the best opportunities to talk to them when they want to share their feelings. Listen to what they have to say, even if it is something you do not want to hear, and offer support and advice whenever necessary.
Remember, if your child feels like you are on their side, they are much more like to confide in you. If they feel like you oppose everything they tell you, they will never tell you anything.