Buying expensive items in vietnam

When i went to HCM in 2017 i had an issue buying a suit in district 1. Having no idea of the cost of fastion names back here in the uk other than google i was pleasently supprised at the apparent price in HMC. However i had great dificulty in even being allowed to try on the suit. when i did find a shop on the street rather than in a shopping center they appeared to be selling dolci cabana suits for 19,000,000 vnd (£634 aprox). This was the price on the price tag and i did clarify with the lady in the store that that was the price and it was for the jacket and trousers. As soon as i tried them on all i could get out of her was "but sir the price" to which my constant reply was yes 19,000,000 for both yes? to which she would agree. 

When it came time to pay she wanted over £3,000 i assume this was the full price paid before the finishing of the suit to be collected later that day. Obviously i didnt pay this and ended after some back and fourth with the lady i ended up walking out.

I did enquire back at the hotel weatheror not the ticket price wasnt the price or if they had missed some zeros off or if there was some tax issue but didnt get any real answer and thinking about it even one zero would make the price far more than you would pay in the uk.

To my question as i am going back in a few weeks now (cant wait!) I am planning on either getting some suits and shirts made in Hannoi or buying some in Hoi An and getting them altered as i only have a day and 2 nights in Hoi An at the moment i may decide to miss out Nha Trang and stay for a couple of extra nights.  Is there a personal shopping service that will help me avoid the above pitfalls or at the very least some sort of translation service.

Second Question is as a British citizan i belive i can claim back the tax how do I go about this please?