People can be polite and generally nice during real life interaction, but when they are at home with the safety of their screen, they can become someone different, and this may or may not be affecting you.
Have you ever gone home and received a message from them, only to be bullied?
I hate you! You are the worst kid in this school! I wish you would die!!!!!!!!
If you don't know how to handle these comments, there are always people to help.
There are many websites that you can use to help you move forward if you have faced any form of this cyber bullying.
There are websites such as Reach Out, Kids Helpline, NetSmartz and many many others that you can use.
To push forward in life make sure that you don't blame yourself for it, be patient because healing takes time, put the phone down for a period of time, keep close with the people that care for you, and keep in mind how good the internet can actually be.