Turn on Silence Unknown Callers: Settings > Phone > Silence Unknown Callers
Block a number from Recents: Phone > Recents > tap the info icon > Block this Caller
Filter unknown senders in Messages: Settings > Messages > Filter Unknown Senders
Block a text sender: open the message > tap the contact or number > Info > Block this Caller
Report junk iMessages: open the message > tap Report Junk if available
Use carrier spam protection apps or services
Enable call blocking and spam protection in Phone settings if your carrier provides it
Add contacts to Favorites so important calls are not missed
Review blocked contacts: Settings > Phone > Blocked Contacts
Update iPhone to the latest iOS version
Avoid answering or replying to spam calls and texts
Remove your number from public listings where possible