Exceeding credit limit and overcharging insurance

Good day,<br> <br> I got a cellphone upgrade for my younger sister. I explicitly told the lady helping me I do not want any credit and she agreed. 2 months into the contract we receive a message saying credit limit of R698 has been exceeded. When I go inquire at the Store I'm told my credit limit was changed from R0 to R698 a month after the contract was upgraded, however I did not request such and neither did my sister who I bought the phone for request the increase in credit limit. Most importantly I did not request request credit. My problem is why provide credit when i explicitly said I do not want any credit. Further more no notification was sent when this limit was increased. I asked for no credit because I knew the phone was for my little sister and I wanted to avoid. <br> <br> 2nd is that I am being overcharged on the cellphone insurance. The phone has a cash value of around R5500 however my insurance fee is for a phone with a cash value of R15000. I feel so **********, overcharged on insurance and put into credit when I said I didn't want it.