Users of Whatsapp sending messages using different, unofficial clients are risking to be permanently banned from the online messaging service. The information comes from the German website Mobiflip which received several complaints from users.
A fair share of Whatsapp users send their messages with third-party apps like Whatsapp+ or WhatsappMD. These apps aren't available on the Google Play Store but offer more features than the official Whatsapp-app. A feature for which many users install the apps is being able to see the "last seen" status from other users while the user's status remains hidden.
Recently Whatsapp started to ban users using third-party Whatsapp-apps and it appears the company has now started to permanently block them. Affected users likely received a temporarily ban or warning before they were permanently blocked.
The permanent block means in practice that Whatsapp blacklists the banned phone number. Which also makes it impossible to activate and send messages using the official Whatsapp-app.
The third-party apps are also no longer developed. The developers ceased development after they received warnings from Facebook stating their apps violate the Whatsapp user terms.
Update: WhatsApp denies it permanently bans users of third-party unofficial apps.