Handsets At Telkom

I took a contract with Telkom for two handsets. My banking details were added on their system and the total amount they need to debit monthly. It turns out that they only deducted for one handset from my account. I went to their stores and called several times in order for them to rectify the mistake they make. They promised with every occasion that they will update their system. One of their consultants said to me at the South gate Branch I must not worry about the other handset I must continue to pay for the one they currently deducting for. My response to her was that I don't want to owe people monies and end up at lawyers because of the mistake they made. Today they handed me over to lawyers and now I'm listed for a mistake they made. They have my banking details why not taking the payments for both handsets as my deductions go off every month. please help any advise.