How do you know someone has blocked your number on IPhone?

When I send my friend a text through iMessage it doesn't say delivered and it has remained that way all day and when I call their number sometimes it will go straight to voicemail and then one time it rang once and then went to voicemail and then I called again and it rang three times and went to voicemail. They have an iphone as well.

Iphone SE won't turn on?

My iphone I bought online won't turn on. Any suggestions? I try charging it but nothing at all. Then, it shows the red bar but it never goes off of that.

Buying a phone that is iCloud locked?

I recently found a phone and they claim everything works great though when you turn it on it says "iPhone is disabled connect to iTunes". Is it possible to get it working again? Would you have to use the iTunes account that was already on the device?