Account thats being billed incorrectly

We are having a problem with our account , our account is never more than R1500 , now its over R2000 and when we go in to see someone to correct their mistake its said sorry thats what you have to pay not our problem its said that we phoned in to give the reading , but we never do that dont even know which number to phone , how can they be so rude towards to old people 67 of age , i am trying to get the help from them to fix it but nothing happens , could you help please