To know if someone has blocked you on iPhone, there are several signs to look for:

• When you send an iMessage, normally you see "Delivered" or "Read" under the message. If this disappears, it could mean you're blocked. Sometimes the message may still appear as blue (iMessage), but without the "Delivered" tag, suggesting the message is not actually delivered to that person.
• If your iMessage suddenly turns green (SMS) instead of blue, it could mean the recipient turned off iMessage, is temporarily screening messages, or you are blocked.
• When you call the person, if it rings once and then goes straight to voicemail repeatedly, it may be a sign of being blocked. Calls from blocked numbers typically go straight to voicemail without ringing on the recipient's end.
• You will not receive notifications on the recipient’s side for your calls or messages if blocked.
• Some other indicators can be no longer seeing "share focus status" or location from them.
• If you try calling from a different number and the call goes through normally, but calls from your original number go straight to voicemail, that confirms you are blocked.

However, none of these signs alone guarantee being blocked because similar behavior can occur due to Do Not Disturb mode, the phone being off, or network issues. The best approach is to look for a combination of these signs. In summary, missing "Delivered" or "Read" receipts on iMessages, sudden green message bubbles rather than blue, calls going straight to voicemail after one ring, and confirmation from trying a different number are the main ways to tell if you are blocked on an iPhone.