Yesterday, I asked my hairdresser to take my highlighted champagne blonde hair to a light brown.
The first color she put on turned it orange and the second turned it dark brown except for my roots (my roots originally were a mousey color). My roots became an orange/brown. She therefore corrected this by putting on a semi-permanent color, which corrected the roots to dark brown, but turned the areas which had been the most bleached originally to black! I hope this makes sense.
Will this semi-permanent color fade, and leave me with an OK color? Is it difficult to lighten this dark brown to a light brown?
I am too scared to go back to the hairdresser, as generally the whole thing is a disaster. I just want my blonde hair back, but I am thinking I need to go to a top salon to feel safe. Please help!

When I use semi-permanents they generally begin to fade within a week to two weeks. That's with home color, but I imagine the salon would be similar. Maybe wait a week and if you don't like it see if they'll pay for you to go to a salon you can trust. They might not but it's worth a shot.

Semi-permanent or Quasi colours that they use in a salon will fade in a couple of weeks or up to 20 washes. It will never completely wash out but your blond should start coming through after just a few washes.