Milton — Thermosteel flask

I have bought thermo steel flask 2 months ago in the nearby city (GUDIVADA).
It was good at starting. But now it was not working properly. I poured hot milk in it.But it was got cooled within 2 hours. The seller told that we can use it for all ex. milk, tea, coffee. But the company is saying that we should not use for milk.I request you people not to buy milton company products. We believe milton is the best company and have spent a lot to buy their products.
if it is not used for milk, then the company should mention it clearly.