Anticipate potential problems or risks with your child
Having conversations about phone use and cyberbullying before any problems arise can set the tone that you are open and will be thoughtful, if they should happen to need you. Remember if they do not come to you at all when things go wrong, there is nothing you can do to help. Define potential cyberbullying situations, so that they know when it is time to seek help (e.g., friends ganging up on them, someone sending an abusive or threatening message or picture, solicitation for or sending an explicit picture or text). Let them know that, even if they feel they did something wrong or broke one of your rules, regarding online use, they can come and talk to you, you will hear them out, and together you will find a reasonable solution or response. (Then, you have to stick to this!). If someone is hurting your child, you want them to come to you, even if they did something wrong or used poor judgment. You can deal with that part separately later.
Ask your child/teen what might keep them from coming to tell you if they are being cyberbullied. Hear their feedback. It is critical. Then reassure them that you will support them first, act fairly, and make thoughtful decisions with them that you feel is in their best interest. Interestingly teens say the two things that most keep them from telling a parent when they feel bullied or uncomfortable about an online interaction or post are: 1) They think parents will automatically take their devices away, and 2) Parents/adults will intervene without their consult and make things worse.