All team members can block a spam conversation.
On the Day List or All Conversations screen, tick the offending conversation then select 'Block sender' from the Actions menu.
You can also do this from the 'three dots' menu when on a conversation page
System admins can block mobile numbers under Clinic Settings in the 'Blocked senders' sub menu.
Notes
Blocked numbers will no longer be able to message the clinic, and any resolved or in progress conversations associated with that number will be hidden
Blocked clients will get no response if they try and send a message in again
If the number is subsequently unblocked, all conversations from that number will be accessible