mtn insurance owing me money and not responding

I got a new contract phone that was ******. The phone was valued at R10800 at the time. I pay for R15 000 insurance. Mtn insurance did not cover the full amount due to the phones value dropping although I am paying for R15000 cover. Excluding the excess I had to pay, I had to pay in R1600 because the insurance authorised too little. They responded on email that I should go to mtn at brooklyn pretoria and they will assist me. Mtn brooklyn said that mtn insurance did not log the problem on the system and therefore cannot assist me. I forwarded all my emails once again to mtn insurance, where the consultant rep**** that they were replacing my phone and not refunding me which tells me that she did not even read the emails. I have asked many times to speak to a manager and have never got a response since October. I have been dealing with this issue since August this year.