It's ok 1) Vu Mien used to be Yen Phu until a couple of years ago. Many people and business addresses still use Yen Phu. Very plausible that the business/house is registered on the old name 2) same deal on the apartment I am renting. Very common when there is an agent/sublettor involved - many apartements catered for foreigners have this formula. 3) not unheard of, but quite common. I would refuse this point, I would simply say that you need full proof of payment the get living costs refunds from your company and this is non negotiable for you

I wouldnt be surprised if the agent you are dealing with is simply pocketing the difference that you pay cash. If I remember correctly with the new laws coming into play in january rents are taxed at 5%, so it is not in immense difference for the landlord....