Help! Professional Color Nightmare!!

Hello everyone!! I'm hoping someone can give me some advice on this one. I went to my usual salon this weekend to get my highlights touched-up (this is a very upscale Salon in Atlanta). They said they had my last highlight formula on file, etc. Well when I got there I had a different colorist (mine was apparently out sick). The new colorist said she did not have my formula on file (or was to lazy to look it up). She then proceeded to die my hair a terrible orange blonde color with almost white streaks through it (my natural color is a dark blonde with natural blonde highlights). It looked absolutely scary! So I went back the next day demanding a new colorist and fix. I asked the new colorist to try to restore my hair to it's natural color. Well she then said she put brown lo-lites in my hair closer to my natural color (supposedly) and then some toner to mellow out the orange. Now my hair is an awful ash gray color with light blonde streaks through it and the ends are BLACK!! My hair is down to my butt (it took me 15 years to get my hair this way). The salon now wants me to come back and have my hair colored again to try to correct the problem..I'M SCARED MY HAIR WILL FALL OUT!! How much processing can you do in one week?? My hair now resembles the witch wigs you buy on Halloween and the top of my hair near the scalp is still orange. PLEASE HELP!!!