Calls go straight to voicemail after one ring or no ring
iMessages stay blue but never show Delivered or Read
FaceTime calls do not connect
Text messages may remain unsent or never show delivery status
You cannot see their profile photo or status updates in some apps
Their location stops appearing in Find My if previously shared
You cannot add them to a group iMessage if blocked
Calls from another number may go through normally
You can still contact them through other apps if only your number is blocked