Help hair color fading

Hi,
My hair color is naturally auburn brown. I got blonde highlights over the summer. I decided around Thanksgiving that I wanted my hair one single color in a dark brown. I went to get my haircolored and they used a filler on it, then used Framesi 2001 5NP haircolor. It came out awesome! After about 1.5 weeks it washed out to a light brown. I got it re-colored using the same forumla, except they used mixed color (ammonia-free) this time. It didnt dye as dark as the first time, but it was still darker then the washed out color. Now, my haircolor has faded once again. I have been using Sebastian's Color survivor shampoo and conditioner that was recommended. I want the color back that I had from day one. I don't think haircolor should fade twice this much! Someone suggested getting it colored again, but doing a clear color shine at the end to lock in the color. Any suggestions or help is much appreciated! Thank you!

I suggest that you dye your hair darker than your natural color so that when it fades it wont be too light..at first your hair will be really dark but then it will fade beccause brown shades always do

i have had highlights a few times before and have had the same prob.. it is b/c you stripped your hair of everything so the hair color has nothing to stick to... thus fading..