iPhone and Outlook automatically synced?

I use Outlook Exchange at work and I access it on my iPhone. Recently, the work email server crashed and IT set up a new account and it deleted a majority of my personal contacts from my phone that are in no way linked to my work email, like distant family contacts, but left some work contacts. It's like the contacts in my phone automatically synced with my work email without any permission. How do I stop it from happening in the future? If I go into settings and to the work email account and click contacts to not sync, it says they will be permanently deleted. Please help!