Cell c not being professional

Hi my name is busisiwe Nkosi. I have a problem with the cell c.i have an contract with them they debt every 20 of the month last month debt the agreement money and on the 25 last month come back in my account searching R43 and why they didn't take the money on the 20th .because now they make up and down in my account as I'm talking my charges is R900 for cell c only .they block my line all my cell c line are not working but I paid the R43 on the 28 of March but on the 31fst they searched the 43 in my accounts pls help me means the charges will go up till 3000 because they make up and down in my account pls help