'Harmful Communication’ or ‘Cyber bullying’ is never okay. If you are getting negative communication, you can definitely ask for advice or help.
Managing your child’s account, or the entire household can easily be done with a Skinny ‘Linked Account’. See here for getting set up.
If you wish to block a number from contacting you permanently, here are some steps for kicking off the process.
Before creating an account with a Social Media Network (eg. Twitter or Facebook), make sure you educate yourself, and keep on top of how to keep yourself and others you know safe.