over charging

We bought a Tv from Lindiwe 2013 and it was R6000 we payed a deposit of R700 and our normal instalment was R450 per month, we honoured our instalment every month and skipped one month and we were advised that the ares were R12.50 of which we recovered that month, having to calculate this means that we have paid r6750 this is excluding the deposit that we paid on the day of purchase, but to my surprise when my mom went to settle the account in store she was told that she owes R6100 for the TV when she asked how come they told her its for insurance, my 1st question is how can insurance be more expensive than the TV and why we were never told about the it from the start,?i spoke to the store manager who showed no interest in assisting me hense she advised the she is new but she will look into the matter and call me but she never bothered her self, as expected.why is Lewis employees trying to rob their customers and giving us false information whne trying to get the sale? i am not going to pay an extra R6100 for a tv that is paying double and for what???? they must remove this R6100 of my account and settle it them self because they never advised us about that stupid insurance ,