City Express 20

I was there on 9-7-19 morning 3:30Am.I was sick and I needed some food before taking medicine.The staff is working and quite busy.I just call him "ညီေလးေပါက္စီရွိလား.He come with impatient face,I know that he's mood is off for working alone and he looks tired.
Once I'm ready for payment the money is not enough.I only brought 2000 KS with me.,I told him to void the payment and The staff said after scanned the barcode he can't void.
I said I've travelled the world and even the Visa card payment can be void on the same date before settlement.I told him that's there is no reason that can't be void.
He become very aggressive and start talking very rude with the customer.I really feel bad about customer service, impatient,his rude words like I'm not selling like in the market, you are selfish and the high enter.
I called to city express store once I get home and the same pick up the phone.I ask his name (His name is Than Naine Win),he recognized my voice. He call back to my number and ask me where are you calling from and he wanted to know what's the problem and why I'm asking his name.
I even feel unsecure with these aggressive guy and I feel shame to the city express to keep such an aggressive rude employee without service mind.
Incharge Sir please have a look the video on your CCTV 9-7-19 morning 3:30Am