Calls instead of SMS - sending a call to consumer's mobile phone.

Solves problems:
   high costs for sending SMS, because calls are twice as cheap as SMS;
   conveys emotions of the human voice to the consumer (there is no such thing in SMS);
   provides a convenient unsubscribe mechanism (press 1 key to unsubscribe from calls);
   analytics (measured by how many seconds of the call the recipient listened to).