Answer:
For one, don't jump into conclusion yet based on no evidence. If possible, you can tell your friend to block the account that has been cyber bullying them or change account.
Step-by-step explanation:
How ever tempting it might be, do not act without any evidences. Ones that can persuade a reasonable person around you. Or else, the report will be treated like nothing, and it might only worsen the bullying. If you get solid proof, go report them. Report their bullying a**