Exchange Sony Z3 for iPhone 6

I hate to do this because I actually love the bank's service on the digital sales. But I am now stuck with a phone that will cost me R10 776 that I cannot use some of its functionality - none of which is my fault. I bought a Sony Experia Z3 on the 21st April 2015. Three weeks later, after trying every possible avenue to resolve the problem myself, I complained to FNB about the fact that I cannot use my web browser on my phone. Support gave a solution that didn't work. They eventually referred me to Sony who offered a solution that temporarily worked - this is after I had to reset my phone numerous times. I would like to exchange this phone to the iPhone and I am not able to do because I apparently the 7 day grace period had passed. It is ridiculous that I have to bear the frustration caused by this phone. I should not have bear any technical problems on a R10K. I am not asking for a refund, I would just like to exchange it for something that is reliable and worth my money. Please help!