Here are a few ways to know that you’ve been blocked:
You can no longer see a contact's last seen or online in the chat window
You do not see updates to a contact's profile photo.
Any messages sent to a contact who has blocked you will always show one check mark and never show a second check mark
Any calls you attempt to place will not go through.
If you see all of the indicators above for a contact, this could mean that the user is blocking you.
Despite the above-mentioned pointers, there is no way to be 100% sure that the contact has blocked you or is dealing with a connectivity issue. According to WhatsApp, they have made this intentionally ambiguous in order to protect the user's privacy when they block someone. WhatsApp will never relay the information directly to a contact that they are blocked.
Apart from just blocking contacts, users can even report them if they think they are sending problematic content or spam.
How to block a user on Android
Open WhatsApp, tap More options icon (three dots) and then Settings.
Within settings Tap Account > Privacy > Blocked contacts.
Then tap Add.
Search for or select the contact you want to block.
How to block a contact on iPhone
Open WhatsApp Settings > Account > Privacy > Blocked > Add New....
Find the contact you want to block, then tap the contact.
Alternatively, the user can block a contact using the following steps
Open the chat with the contact, then tap the contact's name then click on Block Contact then select Block or Report Contact then tap Report and Block, which will report and block the number.
or
Swipe left the chat with the contact in your Chats tab, then tap More then Contact Info then Block Contact then Block or Report Contact then Report and Block, which will report and block the number.
