You're being trolled via the Notice feature in NickServ. Someone does not like you for whatever reason or sees that you will respond to trolling so has chosen to target you. If you don't respond they stop trying and will leave you alone. If you send this to report content or speak to a moderator they will permit a name change for you. Being a victim of trolling is unfortunately a repercussion of using the internet, it is up to you whether or not you want to add fuel to the fire.