Faulty cellphone Nokia Lumia 535

I bought cellphone at Jet Southdale on the 23 July 2015 and I discovered thst the phone is not user friendly and it keeps rebooting and some applications need me to constantly reboot my phone. I work in Cresta and I phoned Jet Cresta and spoke to Mpho to ask if I can come and exchange the phone or whatever way they can help me with, they said I must take it back to the original store where I bought it. when I bought the phone Danisile said I can take it back to any Jet Store if it gives me a problem she did not explain fully that within the 7 day period I must bring it back to Southdale. I explained to the Manager at Cresta that today its the last day for the guarantee and there is no way I can take it to Southdale as I only get home late and the store is closed when I get home so as a customer what extra mile can they do for me. they said there is nothing they can do. so now my question is must I be stuck with a useless phone that I bought for R1.700.00 because I cant get to the shop where I bought while there is a Jet store nearby my workplace? must I suffer because of one *********** staff member who did not take her time to fully explain the process. I want a working phone