Messed up my account during upgrade!!!

I have two decoders, both were on the compact package. I called through to DSTV's Durban Call Centre on Christmas day, i.e. 25th December 2015. My instruction was simple. I asked the agent to please upgrade one of my decoders to the Premium Package. I even read out the smart card number to her. She then confirmed that the pro-rata amount for the upgrade on the one package would be R87.80. I confirmed that it was only one decoder that I was upgrading. On the 29th December 2015, I received an sms asking me to pay R1735.53. I could not understand as my account was fully paid up until the 31st December 2015. I even paid the pro-rata amount for the upgrade on the one package. When I called through today, I was told that the agent had activated 2 premium packages, one on an old de-linked smart card and decoder. I am furious. I had asked Multichoice to unlink the old decoder as it was damaged by storm and re-link a new one. Instead the agent went and activated 2 premium packages. One on a decoder that didn't exist anymore. I had done my duty and went into the multichoice walk in centre and de-linked the old decoder and linked the new one to my name. I should not be paying anything!!!!