This is How to Block Unwanted Calls
Open the Settings app and tap on Phone. Then toggle on the Silence Unknown Callers toggle.
Steps to Restrict a Sender from Received Emails
Ensure that the email address you intend blocking is in your Contacts app.
Open your Settings app.
Under the Threading options, click on Blocked Sender Options.
Select what you want to do with any mail from a blocked sender. Choices are None, Mark as Blocked, Leave in Inbox or Move to Trash.
After you enable that setting, click on Blocked and tap Add New.
Select the contact you want to block.
If Mail is enabled in iCloud, blocking a sender spans across all your Apple devices.