Debit order default

I have been a Tracker client since 2010 and recently changed insurance providers. A consultant from tracker called me and advised that the new insurance company requested an upgrade on the Tracking device in my vehicle to which i agreed. She then advised that its not a new contract and that my installment and service would continue as normal. I had the tracking device installed and a week later i get 6 sms'e on one day advising that my next tracking device installment will be double the amount as there is a pro-rata they need to debit. Never was i advised that the installment would be double and i specifically asked the sales consultant if the debit order will remain as is and she agreed. When calling the call center yesterday to find out why the double debit order, the lady could not even help me and advised that she would have to log a service query which will take 5 business days and even she agreed that the debit order should not be double. As per the consumer act, the breakdown of the fees to be charged was not discussed with me, or sent to me or even the breakdown is not even available. I never ended my contract - THIS IS NOT A NEW CONTRACT. Its simply a continuing of the current agreement, WHY DO I HAVE TO PAY DOUBLE INSTALLMENTS??????