One great thing about iPhones is that they make it simple to block nuisance callers. If you keep getting those annoying automated calls asking if you've been in a recent accident, then you can hang up, go to the call log and block that caller - so long as they're not withholding their number.

But what if it happens in reverse? If you find that you can't get through to a particular person after multiple attempts, is there a way to tell if they have blocked you on their iPhone?

Similarly, if they don't reply to your messages, can you see if it's because you're blocked or because they have Do Not Disturb enabled instead.

Before we get to the tips, know this: it is tricky to know for sure if you have been blocked. But hopefully, you'll be able to find out one way or another.

The most likely scenario is that you're being paranoid, and the other person just hasn't got around to replying to your message or calling you back.

But, if it's not all in your mind, here are some signs that you might've been blocked on an iPhone. If you need to be 100 percent sure, you'll need to ask them in person.

What happens to a blocked phone call?

To test what happens to a blocked call, we blocked a number and monitored the experience on both phones. When calling from the blocked number, the caller hears either one ring, or no rings at all, but the other phone remains silent. The caller is then informed that the recipient isn't available, and is diverted to voicemail (if that service is set up by the person you're calling).

There doesn't seem to be a reason why the number of rings varies, but if you hear two or more, you can be pretty sure you haven't been blocked.

Note that you can leave a message if someone has blocked you, but the blocker will never be notified of the message. It does appear at the very bottom of their voicemail list in the Blocked Messenger section (if they're on a carrier that supports visual voicemail such as O2 or EE), but most people probably won't check there.

What happens to a blocked text message?

Texting someone who's blocked you works as you would expect. The message sends as normal, and you don't get an error message. This is no help at all for clues.

If you have an iPhone and try to send an iMessage to someone who has blocked you, it will remain blue (which means it's still an iMessage). However, the person you've been blocked by will never receive that message. Note that you don't get a 'Delivered' notification like you usually would, but this in itself is not proof that you've been blocked. They could simply not have any signal, or an active internet connection, at the time you sent the message. 

OK, so have I been blocked or not?

The call is the best source of evidence to determine whether or not you've been blocked by an iPhone user. The key is that you will always be diverted to voicemail after exactly one ring - if they were declining your call, the number of rings would vary each time, and if the phone was switched off, it wouldn't ring at all.

Also keep in mind that Do Not Disturb will also cut you off after exactly one ring, so don't get too worried if your calls aren't going through at 3am. There is a Do Not Disturb setting that allows the user to specify that repeated calls are allowed through so you could always try again right away - just make sure your call is urgent, or they may block you for real this time!

Finally, we would like to repeat that this isn't an exact science, so don't make any angry scenes without knowing for sure. Also: chill out, relax, and try not to worry about it. If they've blocked your number, hey, who needs them?

(If your problem is the opposite and you have an iPhone and want to stop an annoying caller ringing or texting you, here's how to block a number.)