Fone broken factory fault

My name is Thabiso mokoena from kagiso in krugersdorp i bought i took a fone from pep wth a contract of fone yami i only used it for 3monthz the other 2months it was gvng me problems i havent been using it but paying for it,i took it back then this guys said they took it to voda to be fixed came back stil the same now wen i took it back for fixing they say i must pay 4k and i am paying this fone monthly R435 so i am so angry i am paying for somethng i am not using i just want tge money i paid or new fone