Registration not processed

I am very disappointed in unisa. Im in my final year of study with only two modules left. I paid my initial minimum payment for registration and it never processed. And a few weeks later I receive an email in firming me that my registration is canceled because I did not pay the initial minimum payment. So now I have to wait all year for me to register next year. I tried calling the registration department without any success of reaching them and when I went on campas I was told they are on strike. Please help