Horrible customer service

Yet again this month, problems. I was debited excessively last month, then was told I have a credit which will be app**** for this months invoice... Mind you, I was debited more than the monthly invoice amount credited... But never mind this. This month, guess what.. I am disconnected, although the agents say they see my account is up to date but their billing department needs to rectify because they can't... I have been calling for 4 days now and same response... "The billing department", what about your consumers????? I just can't keep doing this... Kant when does the billing department actually work? Better yet where are they cause their call centre appears to be in another country.. Customer service is horrible. .. On top of this, each time you raise a point, the agents hang up..