Strip Black Hair (Dyed)?

I have Schwarzkopf Deep Black 99 in my hair and I want to get it stripped to put in Red Passion 43 (No you can't dye over the black I've already contacted Schwarzkopf they said it themselves.) Does anybody know what I can use to strip my hair, how often I use it and what damage it will do?

Strip Black Hair (Dyed)?

you have to go to a professional salon, usually dye strips are so strong they dont sell them in stores, but salons have them and can use them the correct way...