Peanuts, something I learned to do when people try to cross my boundaries is say "I feel bad when..." "I don't like it when..." "It hurts my feelings when..." Try not to use the word "you" if you possibly can. That automatically puts others on the defensive. Keep it strictly about YOU. You may not get what you need, or get them to stop at first, but keep repeating it every time your boundaries are crossed. You may find that you'll have to get more assertive, but that river can be crossed later.