Can’t turn passcode off on iPhone?

I used to go to a university that required a secure exchange email account and because of the account I was required to have a passcode on my iPhone and it was required to lock immediately. I graduated and deleted the secure email app, secure hub and secure web but it still requires the same strict passcode settings and other options are greyed out. How do I turn off my passcode? After deleting the apps I have trying restarting my phone and I have tried a hard reset and still no change.