If the iPhone settings are grayed out and you are not able to change or select them, this could be due to restrictions on the phone. Note: Depending on IT Policy, the client may need to enter a passcode when selecting Restrictions.
To check the restrictions settings on the iPhone, follow these steps: Settings > General > Restrictions > Change > Accounts > On/Off. The restrictions should be set to On. If they are set to Off, follow the steps listed below:
1. Change the restrictions settings to On and click save.
2. Delete the Exchange account.
3. Turn off the phone.
4. After 1-2 minutes, turn the phone back on.
5. Set up the Exchange account that was previously deleted.
You should now be able to access the settings that were grayed out.