****** WITH RAM

I bought a Mecer Z140c notebook last year 21-12-2019 and the manual says it's a 2G RAM but it's not it's 1.50 RAM and now I cannot update to the latest version of Windows 10. I paid R3499 and want the rest of my RAM. I FEEL THAT I HAVE BEEN ****** BY ONE OF THE SO CALLED BEST IT COMPANIES.