Apple India — I am complaining about my IMac 4k

Address: 400703

I was straight away fooled by apple store when i went to buy imac they showed me a display product and then i purchased it for 1lac 20thousand and now it says it's the old one late 2015. I bought it last month i have all the bills. I am totally dissapointed also because i can't even upgrade my ram. The salesman while buying he said that i can upgrade it later. Today i am finding difficult to do my work that is video editing. While the time of purchase they said its the fastest imac machine for video editing but turned out to be a wrong.