Hi Fatima
I understand if you don't want to get into an argument about this, but if you bought it direct from Apple over the internet you shouldn't have a problem. If you exercise your 14 day return clause you also usually get another 14 days to send it back - again if you bought it direct.
I have to say that I always find Apple direct very fair and a model of consumer excellence.
There are also plenty of model letters you could use to help you on the Which and Citizens Advice website.
However if you want peace of mind I would send it back within the 14 days and at the same time order another new one.
If that too exhibits the same problem - as mine did - send that back as well, and perhaps look at another model or another brand.
I have always been a big fan of Apple with iMac, iPhone, MacBooks and iPads, which I have bought for many years.
Personally however I feel that the company is now, in some cases, producing goods that DON'T just work', and do not have the quality they once did.
Much as I hate Windows or Android, I am looking at them as alternatives for my next products.
Anyway I hope you get it sorted to your satisfaction.
Regards
Ron