CA nonresident and remote work

I worked remotely as a 1099 in CA for 6 months from my home in Nevada. I never set foot in CA. The company I worked for withheld $13,044. I was assured by them that I would get that all back. My withholding was reported on a CA Form 592-B. Now that my taxes are complete my CA refund is only $3541. To the best of my knowledge I've made no mistakes and noted where asked that I was in NV the entire year. Why am I not getting all my withholding back? Thanks in advance for the help.