Cannot install whatsapp on Nokia Asha 503

I bought my phone in June 2014 and used whatsapp until February 2015. When I complained about the screen freezing,pic not uploading, Vodacom said that is's the software that needs to be upgrated. Vodacom send my phone in 5 times and everytime it comes back they couldn't install whatapp. Vodacom just says that whatsapp is a 3rd party and I must phone them, but in the same breath they say that all the Nokia Asha 503' got problems! Nokia in 3 Rivers doesn't want to send in my phone because they say that Vodacom must have given me a new phone after the 3rd time they've send it in. I bought this phone specially for the whatsapp. Vodacom in the VaalMall Vanderbijl Park said that I must buy a new phone.