Whatsapp update failure

Last year I bought my youngest children each an iPhone3G. They use it with great pleasure, but suddenly they can't get access to Whatsapp. Due to you (Apple) not supporting updates of iOs to that level needed! I recognize your urge to want them buying new iPhones, but this is so unfriendly. To my children who are suddenly cut out of their contacts with their friends ánd to the environment! This can't be the way to make this world a better place!