Vinaphone

You should complain to Vinaphone ... who send them to you. The ones that bug me are the ones early on Sunday morning.

Just as responsive as speaking to a concrete wall.

I use call management software that filters out these things. t also converts all out of hours to silent SMS messages.

ONE GOOD thing Vina has is the 365 Plan (free) which requires you to make one all a month and skip refills (until needed). I put VND100,000 in my daughters emergency handset almost 5 years ago and have still put no more money in it.

Go to Vina on Nguyen Du and they will activate for you.

The people at Vinaphone or the young Vietnamese tech gurus can turn that off for you. 

I went through the same thing 2 weeks ago, when I bought a Vinaphone number.  One of my local tech Gods did something and all those annoying text messages went away.