Raising Premuims twice a year!!!!!!

After a hour conversation with std bank to adjust my homeloan premium,they sended me a updated policy with new figures for next year to come.Now i get a email after a month again that my premuim is raised with another R250 for nothing,if i call them after 15 minutes on the line they answer ,only to take my details to phone me back later because they have high call volumes.But why is my premuim raised twice in one year??????