Xbox help please

My cousin has been harassed by 2 guys online to the point she is in tears. She is only 12 and these keeps keep going around being blocked by making new accounts and each time we report this nothing happens to them. We have tried everything you guidelines told us to do but it won't stop. I have videos proving what these kids have said if it helps. She does not know Anything about reporting which she has on both profiles now.

:)