Blocking someone on Telegram usually means that you will no longer receive messages, calls, or notifications from that person. However, there are instances where you may still receive messages from a blocked contact. This can be due to a few reasons, including:
Old messages: If the person you blocked had sent you messages before you blocked them, those messages will still be visible in your chat history. You may continue to receive notifications for those old messages even though you have blocked the contact.
Group chats: If you and the blocked contact are both members of the same group chat, you may still receive messages from them in the group chat. However, you will not receive any direct messages from them.

Different accounts: It is possible that the person you blocked is using a different account to contact you. This could be a new account they created or an account they had previously created and had not used to contact you.
If you are still receiving messages from a blocked contact, there are a few steps you can take to prevent this:
Delete old messages: If you are receiving notifications for old messages from a blocked contact, you can delete those messages from your chat history. This should stop the notifications from coming through.
Leave group chats: If you are receiving messages from a blocked contact in a group chat, you can leave the group chat to stop receiving their messages.
Report the contact: If the person you blocked is still harassing you or contacting you through a different account, you can report them to Telegram. Telegram takes harassment and abuse seriously and will take appropriate action against the offending user.
Verify that the contact is blocked: Finally, it is important to make sure that the contact is actually blocked. To do this, go to your Telegram settings, select "Privacy and Security," and then select "Blocked Users." Make sure that the contact you want to block is on this list. If they are not, you may need to block them again.
In conclusion, if you are still receiving messages from a blocked contact on Telegram, it may be due to old messages, group chats, or different accounts. To stop receiving messages, you can delete old messages, leave group chats, report the contact, or verify that they are blocked. By taking these steps, you should be able to effectively block unwanted messages from a contact on Telegram.