Paytm Mobile Solutions — wrong product delivered-asus laptop

Oder no: [protected]
I order for asus laptop in oct 2017. It says that "expandable memory
1 x so-dimm socket for expansion, up to 12 gb sdram".in march 2018, i went to asus service center to add 8 gb additional ram. Asus service center engineers confirmed that it can maximum have 8gm as it doesnt have any expansion slot.
When i contacted paytm service center, they are saying that you should have informed within 10 working days.
How can open (Unscrew) a laptop to check if it has all promised hardware configurations, unless i have some problem and i go to service center? In short, return timelines shouldnt be applicable on such problems where paytm is making false promise on their website.