how to block phone numbers

Hello raneen81,

See the steps below to block phone numbers in macOS Messages:

"Block messages from a specific person or number

1. In the Messages app  on your Mac, select a conversation.
2. Note: The conversation must be with one person, not a group. Instead of blocking a group conversation, you can leave it.
3. In the menu bar, choose Conversation > Block Person, then click Block."

Block messages in Messages on Mac - Apple Support

Cheers.