Such bad service, with no proper telephone numbers to call

I paid up my account on the 3rd of August and I have been trying to get hold of the department responsible for ITC all in vain I keep receiving calls from their call centre that I am owing. This company has no direct number that one can call and get assisted by someone who knows what she is doing. Can someone with information where their offices are kindly help, I am so frustrated yet I v paid up the account