Tell everyone: cops, school, parents, if you can find proof that it is from him that’ll be even better for getting repercussions and/or help. Unfortunately, when it comes to cybercrime like this, it is extremely hard to have anything truly done about it. So please keep taking receipts, but tell everyone you can who you think will be able to help. File reports to start a paper trail as it keeps happening, this should eventually be able to be treated as stalking, etc.