premise: A missed call is a telephone call that is deliberately terminated by the caller before being answered by its intended recipient, in order to communicate a pre-agreed message without paying the cost of a call. For example, a group of friends may agree that two missed calls in succession means "I am running late". The practice is common in South Asia, the Philippines and Africa.
hypothesis: Pre-agreed missed call messages are only practiced in 3 countries.
reason: The context  does specify if the countries mentioned are the only ones using this pre-message system.