How to Subscribe:
Though the service is in test phase and not commercially launched yet, you can still subscribe to it :
To subscribe send Sub to 9211
To add a number in block list send Block <space> Number and send to 420
To delete a number in block list send Unblock <space> Number and send to 420
The service is in Test phase so its possible that these commands may/may not work.
Note:
Update: Rs. 19+tax are charged when you subscribe to this service though Warid representative still saying it costs Rs. 25+tax.