Fed up customer

I have had to complain every month, same problem for the past three months. I have cancelled subscription for one of my lines for the past 3 months now and I am still being billed. Vodacom is the worst service provider, I have been so patient with them, and when you call you will be taken from pillar to post. Even if you decide not pay you will suffer because they will disconnect your other line. I am so fed up with this, all they know is to apologies but still make the same "mistakes" over and over again.