WHY SHOULD THE CONSUMER PAY - TAKE RESPONSIBILITY

We recently upgraded my contract including Insurance from Vodacom, Vodacom gave us a price for the Insurance and they debit my account every month for this amount given on the new device, then my phone got ****** - Vodacom have now advised that they have made an error on their side and that they were billing us the incorrect amount on the insurance and we have to pay R900 ONTOP of the excess to replace my phone - WHY IS THAT MY PROBLEM WHEN VODACOM GAVE US THE INCORRECT INSURANCE PREMIUM AND HAVE BEEN DEBITING MY ACCOUNT FOR THE WRONG PRICE since the contract was renewed. We take insurance out to prevent this kind of frustration and the finance inconvenience NOW i have waited for nearly two weeks since my phone was ****** and VODACOM still cannot assist me, i left a message on Saturday for a supervisor to contact me and i am still waiting on this - YOUR MISTAKE VODACOM, you should be held liable for the R900 back pay on the insurance premium as this was an error on your side - it would be greatly appreciated if somebody can get back to me with a solution to this problem - why should the consumer pay for the error of Vodacom - TAKE RESPONSIBILITY