You have a little more time to use the WhatsApp app on BlackBerry OS and Nokia S40 or Symbian 60 unlike their statement in January about removing support for those platforms by December 2016. The WhatsApp Support Team shared this in a post.
Android users with Android 2.3 or earlier and those with Windows Phone 7 or iOS 6 will still get their access removed by the end of this month.
WhatsApp cited the ending support for these platforms as them not being able to offer the company the capabilities needed for future features in the app. Users using BlackBerry (including BlackBerry 10), Nokia S40, Nokia Symbian S60, Android 2.1 and Android 2.2 and
Windows Phone 7.1 will be required to upgrade to newer devices that can support new WhatsApp features. This may be a setback for those who can’t afford new devices, especially in emerging markets like Africa who are its biggest consumers, as you can see from this chart on WhatsApp users by region at the end of 2015:
It looks like you have no other option but to change your phone.