Definitely go back, it's verging on blue.
Do you follow Cher Webb on social media? She's a make-up artist and pretty much has the colour you are after, a cool icy blonde. She has posted tutorials before about her hair and the products used (purple shampoos etc). I'm very envious of her hair but I don't suit being that blonde.
I'm guessing you would need a full head bleach then the purple shampoos. In the meantime, as horrible as it is and been there myself - complain.