- If the arbiter really signed with your instead of his signature, then he just committed a crime (forgery of documents). He could have signed with his signature as proof that he confirms result and everything on scoresheet.
 - If the arbiter really forged your signature, ten as a first step you should lodge a complaint against the arbiter with the tournament organizer, then, if necessary, with the federation that organizes the tournament. Depending on how serious the matters are, the police may be involved, but most probably you can solve it peacefully.
 - Obviously in parallel, you still make your complaint known to the appeals committee desk.