Encounter with Ms PRC

I was making payment at the Nubox, Tampines Mall and decided to converse with the staff in mandarin because I heard her accent from her conversation with her colleagues, that she is probably from PRC.

Me (pointing to the screen protector which I was able to purchase): 这个是可以用 front and back 的对吗?
PRC (instructing her colleague): 看一下这个适合她的电话型号吗.

She repeated this thrice.

I began I speak in mandarin and said: my question was 'does this comes with the front and back cover, not some random things like whether this protector is for my phone model or not."

Seriously, you can't even understand simple "front and back" English, you should really brush up your English.