Help! Hairdresser dyed roots nearly black and its not faded at all!

[GertyTheGert]

I have (grey) dark blonde/light brown hair and I just wanted the roots done and literally a couple of foil highlights BUT for some reason I didnt spot in the salon mirror/under their lights, she has dyed my roots nearly black! Washing with Head & Shoulders hasnt lifted it one iota! Anyone know a way out eg shall I ask for highlights thru to the roots to break it up or can nil be done because its nearly black? Anyone any ideas? :-/

I think, when a hairdresser did that to me, I had to pay to have all the dye stripped and a new colour put in

SOLE MIO! Why is dyeing hair a nightmare nowadays?!!!! Oh well, I probs will have to do that (& thank you for the advice!) as since 28th when I first posted have washed with Head & Shoulders (and 5 fizzy Vit C tabs added as per internet info!) every day, but has only faded to very dk brown!!!