Overcharged account

i am very upset that telkom is continuouslycharging me for a sim that was issued to me with a package that i took in December 2014.The sim card has a limit on it and when the limit is over there no call that can be made from the phone.I am being charged for call from that phone and this has been queried before and it was sorted out and now i am being overcharged again.How many times do we have to go through the same query.Can someone in the account department get their act together and sort this out.I am continuously going to telkom office to lodge a dispute month after month .Is this how we must now manage my account.i cant believe that your accounts department is doing their jobs properly