When you buy something new, will there be a warranty?

Fake goods - it's unlikely you'll get any joy.
For the future, buy direct from the dealer's service dept.

You can always go same shop to complain

The only warranty I am aware of is, "Thanks for the money, sucker. Now beat it!" 

I send my Vietnamese wife and, after an hour of listening to her, they are happy to refund our money : - )

Reminds me of a guy who bought a Nokia phone from a shop in D1, he was assured it wasn't fake. Two weeks later he returned the phone to the shop and was informed by another seller that it was a Chinese copy. He produced a receipt showing what he paid for it, the price matched the price of an original Nokia.The shop had to refund him.

Warranties are certainly available when buying from shops such as Thế Giới Di Động, which specialize in electronic devices and accessories and are fairly ubiquitous nationwide. The goods are genuine and the service is usually good. Their main drawback seems to be limited selection and range, as each branch is rather small.
https://www.thegioididong.com


Phong Vu is another one.
https://phongvu.vn


Larger cities have department stores that sell household appliances, both from VN and abroad, when you need a fan, rice cooker, kettle, etc.

The supermarkets usually have these kinds of things upstairs as well.