Terrible customer service at Telkom

I have sent my bank statement to three different consultants at Telkom mobile to prove that the monthly instalment of R799 for my phone was paid on April 5. Since then Telkom did not debit my account for May and June instalments; now they have been deducting huge amount on my standard bank account. I have sent the statement 2 weeks ago to fix the problem but no consultant is willing to help me.