I bought a used SP3 and I checked the (basic) warranty after I registered the device. I found out I'm good until mid-2016. Now, I know that the wifi issues have been discussed to death and I have tried some of the methods. It worked! But it sometimes doesn't. Last time it happened, it worked for around 2-3 days, then it's stopped connecting to the internet even though wifi said it was still connected. When it didn't work, I had to wait a bit or restart. So, I was wondering if it's possible to go into the store and ask to exchange for another one without the receipt and box? Thank you!