How to know if someone blocked you on an iphone?

I have been texting this guy a lot lately and he just recently stopped replying, I have sent him multiple messages and the message says it has delivered but he does not text back. I know he has his phone because he has been active on his social networks.

If he blocked you, there's really no way to know if he blocked you.

1. Pick up the phone receiver of the phone line that you want to test for blocking.
2. Dial the number of the person you believe may have blocked your number.
3. Listen to find out whether the phone call goes through as normal. That is, the phone rings and an answering service picks up or the phone rings and the person receiving the call answers. If either of these two things happens, your phone number is not blocked from that number.
4. Check any recorded messages that you hear when you dial the number you believe you are blocked from calling. Your phone number is blocked if you dial a number and hear a recorded message informing you that the user you are calling has blocked your number.
5. Call any other phone numbers of people you believe may have blocked you. Repeat Steps 3 and 4.

Jocelyn is wrong, calling has nothing to do with texting. If they blocked you on text then you can't tell.

If you block your number and call the person you believed blocked u the phone call will go through as normal