Terrible service!!!!!!

In 2013 I bought a samsung s4 at cna cavendish square.Today I wanted to take the phone in for repairs at smartlab as it was still within the 24 month samsung warranty period I had to produce a proof of purchase I never checked the proof of purchase so when I got to smartlab, they informed me there was something wrong with the serial number.So we went through it and there was no imei number on the proof of purchase only the serial number on the box was on it.I than called cna cavendish and the lady informed me that I can go to any cna to get a reprint. When I got to canal walk cna the lady behind the cellphone counter was so rude and had a very bad attitude making me feel like an idiot after the whole ordeal she said I must go back to cavendish cna as only they can help me.I must now run around to sort out the mess that their consultant made.I must now drive to cavendish which is far from where I live and in my time and I can only do it on a weekend.Im am so frustrated, and to top it all the manager was on a smoke break outside for the whole time ive been in the store.its almost as if they are doing me a favour I dont feel like a customer at all