please help!

Well your local salon is wrong. Its more a question of how much damage it will be to bleach it outand recolor w/ a shade matching ur natural color. But w/ that said, what you should do is find another salon in your area, with a good colorist that can remove it w/ a color remover or bleach it, but bleaching is extremely harsh esp. when trying to remove black. There's only one good reason that i can think of as to why ur salon says it "can't be done" and that's if you've been coloring ur hair w/ Feria black. (That's becuz it's a metallic dye which would make the bleaching/removing process extremely tricky)

If you want to, you can go to your local beauty supply and get l'oreal Colorfix to remove the black, but be aware that it might take more than once to take out the color. From there u can recolor in a light (ash) brown, becuz ash counteracts any orange tones that might appear in the hair. I suggest clairol complement color, w/ 10 vol. developer if ur just depositing.

I would NOT, however, advise you to bleach it urself at home. This is best left to the professionals. If you do call up another salon, ask them if they have Igora Modulat. Its supposed to be a less harsh color remover that takes out permanent and semi- hair color w/ out bleach or peroxide. Btw, u haven't mentioned whether the color on ur hair is semi-permanent or permanent. There is also a gentler method of stripping the dye from ur hair by pulling it through a soap cap; this involves mixing bleach and shampoo at leaving it on ur hair for a small amt of time, and then washing it off. Though this most likely will not take out all the build up of black dye in ur hair.

Also, in the mean time, u could use an anti-dandruff shampoo like Head&Shoulders to "fade" the black in ur hair somewht. A lot of pple like to use Prell in this situation, but it strips ur hair of all the moisture.

It's best to look for a salon that has good colorists really knowledgable and they should be able to get u back to light brwn w/ out too much damage. Well good luck.

Be aware that Colorfix will likely turn your hair orange or yellow.  This is a good thing, because it removes the darker dye, its not so damaging, and it's easy to dye a light brown over this shade...I just didn't want you to be surprised or think it had gone terribly wrong.  You may have to Colorfix more than once to get it all the same color, then you will have to dye it with an ash shade just like Veronica F said.  

Do you have a Sally near you?  It would be better if you waited until after you used the colorfix so you could see what color your hair came out first, then bought the dye at a Sally or other beauty supply so you can get the appropriate base color in your dye.  If it comes out orange you'd want an ash dye with a blue or green base, and if your hair comes out yellow, it would be better to get an ash dye with a violet base.  It's worth being careful here because with your hair yellow, the base color has more of a chance of showing if it's not counter to what you've got (in other words, you know for sure you'll be fine if you use a violet base on yellow hair). 

If you don't have a beauty supply near you, and you go for a box color, it may be worth calling the company that makes the color to ask what is the base color of the dye (since it's usually not written on the box with those) to make sure you get one that will give you good results.  If you don't want to do that, at least do a test strand. 

As far as permanant vs. semi perm, I haven't tried semi perm myself, so I can't tell you.  Anyone else know?

Thanks for the advice!

just one more question! could you recommend a timescale for doing this? For instance, how long would i have to leave it before doing another colourfix if it takes more than one? And then after having done colorfix can i dye it straight away?

Just make sure you thoroughly, VERY thouroughly, get all that colorfix out of your hair before re-dyeing. Otherwise, your color will end up re-darkening to or close to the black color.