I am sorry to hear about your hair colour problem. Having read your question I think what has happened is that the initial colour choice of the stylist was wrong. Even though you wanted to go only a couple of shades darker this is one of the trickiest and most delicate colours to achieve on highlighted hair. It takes a true colour specialist to get a natural looking dark blonde without greenish or orange tones appearing.
I would let your hair rest for a while and get it into good condition by having treatments to moisturise and to put back some protein you may have lost through colouring.
Do your research into finding a colour specialist in your area, this can be done on the Internet or the best way is look at peoples hair who you like and ask them where they go. They should be flattered and will tell you who their colourist is. Go have an in-depth consultation with them and show them examples of what you would like to achieve, explain to them the history of your hair so that they can build a picture so they know where to begin.