Hey. As much as I can understand here he seems to be trying or did already scam you. I doubt that the administration would contact you via any unofficial account or ask you for any personal information about yourself so try to avoid sharing it. Since you said you already sent it to them try to delete it as soon as possible and inform a person of authority in your life like your parents or someone you trust about it.
Please Note: I am not part of the GrandRP support team, I am just bored and like to help others.