Proof of purchase not received

I received my Samsumg cellphone from samsung store in Brooklyn mall Pretoria on the 29th of July 2015 which was in for repairs but i haven't received my original proof of purchase since. I have been going in and out of the Samsung store for months now, they keep on giving me stories and telling me that they will let me know when they will get the proof of purchase. The problem with the phone was that it would restart 10 times or more in a day. It still has the same problem after coming from repairs. So I would like to take it back to Game where I purchased the phone, but they need proof of purchase. Now Samsung store says that they cannot give back the original proof of purchase.