On occasion, you may suspect that someone has blocked your phone number, either accidentally or intentionally. When sending an SMS or an iMessage (if you are using an iPhone), it is impossible to determine whether or not the recipient has received a message. As for phone calls, it is slightly easier to see if you have been blocked.
How to know if someone blocked your number
Without hiding your number, try to call the person. If you are redirected to a voicemail right away after a few ringtones, the person may have turned off the phone or enabled the Dot Not Disturb feature. In that case, you need to find out if the same thing happen with another number. Then, you should try to call again in a few hours to figure out if it is still busy.
Try to call from another phone, or mask your phone number before calling. Then, you may have been blocked if the person answers, or you can hear more ringtones before being redirected.
How to block a phone number
If you want to block one or more phone numbers, you can check how to block unwanted calls and messages on Android and iPhone.