I've dyed my hair 4 times trying to hide my highlights but it doesn't work! will black hide it?

i had highlights in april and in march i was getting my retouch but my cosmetology instructor messed it up!! she bleached over the old highlights 2 times and said it was ok! (is it really ok to bleach over hair that had already been bleached?) then i had to dye it a light red and cut off the damaged hair then i dyed it with a semi permanent dark mocha brown but it washed off. and recently three weeks ago i dyed it with the CHI permanent dark mocha brown but it did not hide my highlights!!! i know all this dyeing is not good but i just want to hide my highlights. Waht can i do?? will a black dye cover it FOR GOOD??