Selling bad/ broken phones

Bought a cell c cellphone from jet. Top of the range according to the sales people. Had it for a month then the paw paw hit the fan. Maps do not work at all, unless you stand inside cell c shop. Blurring, freezing etc. Took it to the store and immediately they know about the problems. I can unfortunately not give my fine in for two weeks. I use it for business, banking etc..they have no lend phones.. What am I suppose to do...bad service if your phone do not work like it should..not even cell c know what is wrong..