Can't add anyone to a shared calendar

Unlike some Android devices, contacts are neither stored locally on an iPhone nor in SIM. They are synced to an email account that you had Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other

If Contacts were on iCloud, try this --> Restore contacts, calendars, bookmarks, and more using ...

Else Add the email account that stores your contacts in the IOS mail app and enable Contacts. If you have a corporate email account added through a profile on your device, please check with your organisation's system administrator.

lis266 wrote:

all of my contacts are greyed out

It would be better if you can please re-post with a screenshot, in order to understand the phenomenon better. Images/pictures speak louder than words. 

Please understand this is a public forum: While attaching a Screenshot, do not provide any personal credentials, such as IP address, Card detail, email id, apple id, IMEI number, Serial Number, Phone number, Order ID, if you are sharing a map ensure your location is not identifiable, etc.