Facebook's WhatsApp instant messaging service is ending its $1 annual fee to boost the number of people who use the mobile app. Co-founder Jan Koum stated at this year's Digital Life Design (DLD) conference the move will allow people without access to debit and credit cards, to use the service. Most of the company's competing apps are already totally free.

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WhatsApp is available for several platforms including Android and iPhone devices. The company shared in a blog post that almost a billion people worldwide use the application on devices such as smartphones and tablets, according to Yahoo.

WhatsApp also added that the yearly charge caused apprehension among users without a debit or credit card number that their subscription would end after one year. It also opens markets to increase add revenue.

The $1 annual fee officially ended on January 18, Monday, according to Engadget.  However, it will take one or two weeks for it to be applied to all of the app's versions.

Facebook Messenger is the social network's other free chat app. It almost has as many users as WhatsApp.   

A big issue will be how the company will earn revenue without charging annual fees. WhatsApp will likely use its customer base to make new business partnerships.

However, the company has pointed out it will not add mobile ads. Instead it will test tools for using WhatsApp to communicate with businesses and organizations, which could later replace SMS messages. They could include notifications about illegal bank transactions and delayed airline flights.

The WhatsApp messenger app was launched in January 2010 by two former Yahoo employees who decided to develop a chat app after realizing Apple's App Store was about to create an app industry. Koum chose the name WhatsApp because it sounds like "What's up?"

The other co-founder Brian Acton encouraged Koum not to give up when the application kept crashing.  WhatsApp 2.0 was a stabler version and rocketed the number of active users to 250,000.

Facebook purchased WhatsApp in 2014 for about $19.3 billion. An irony is that Koum and Acton had applied for jobs at the social network after leaving Yahoo, but were not hired.