If a subscriber wants to unsubscribe or opt-out from a premium billing service, he or she is required to send ‘STOP’ to the service short code. Eg ‘STOP’ to 1901. You can also unsubscribe from specific services on a shortcode by texting STOP [Service Name] to a shortcode. Eg ‘STOP LOVE’ to 1901. This is the mode of unsubscription supported by most Mobile Network Operators.