Useless and incorrect billing not sorted out

Incorrect billing for a second month, even after I phoned to ask for a dispute. After 3 weeks it has still not been sorted, my money has been taken incorrectly again and now they owe me over R1000 and say that the 'case' is still open. That just because someone forgot to cancel the 'old' line to my old house, and just added the new line to the new house to the account. :( Totally unacceptable!