Many WhatsApp users have only a month left on the service, with the instant messaging app set to end support for a range of older mobile phones at the start of 2017.
Despite announcing the news earlier this year, many users are only just becoming aware of the impending change and have taken to social media to express their panic.
The Facebook-owned company announced in February that support for older versions of Google's Android - Android 2.1 and 2.2 and Windows Phone 7.1 will end this year.
Support for the operating systems of BlackBerry including BlackBerry 10, Nokia S40 and Symbian S60 were also initially due to end but these platforms will now be supported until June 2017.
WhatsApp now has more than one billion users and said in their original blog post that they want to focus their efforts on the "mobile platforms the vast majority of people use".
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The firm said that when WhatsApp started seven years ago more than 70 per cent of smartphones sold at the time had operating systems offered by BlackBerry and Nokia.
But as of 2016, more than 99.5 per cent of operating systems used on mobile devices are now offered by Google, Apple and Microsoft.
WhatsApp has recommended that those with affected devices upgrade to a newer Android, iPhone or Windows Phone before the end of 2016 to continue using the service.
