How can I fix highlighted hair?

So I went to the hair salon. I have black hair and I asked for highlights but she barely did any 😡 she grabbed a lot of hair and just used a very thin amount of hair to highlight it so I have more black than highlights and the highlights are platinum so I want to know how I can fix this on my own? Or can they fix this at the hair salon? Can they grab some of the black hair and add highlights to it?