What I experienced in India was that a brief message was automatically added as a caller tune to all outgoing calls.
To grab attention, the message starts with a 'coughing' noise and tells about critical information like helpline numbers and social distancing.
However this burst lasted only for 3 days before people got irritated. This helped every population strata to be at least aware of the situation.
Extending the idea, smaller 15sec ad style messaging may help to spread the idea.