If you try to contact me with a phone call, you might as well send your message into outer space. You'll have better luck getting a response from aliens.

99% of incoming calls to my phone are spam. I won't pick up an unknown number unless someone has already contacted me and told me to be expecting a phone call, or it's a call from someone I already know (people I already know don't call me either).

That is to say, your mileage may vary on what counts as a "suitable medium".