4 years ago I got a phone number from Dtac. Which I used regularily on trips to Thailand 

This year I got a new phone. Surprise surprise. It only worked in 3G. Also I was dramatically overcharged for data on a daily basis.

I went to the Dtac shop. They told me I had a Thai person phone number. Patently untrue as I had got it myself from the same shop.

If I wanted my phone to have 4G I would have to show my passport. Something that was not necessary when I originally got the number.

Interesting!

Not sure what the question is but indeed passport/id card must be recorded for phone cards now as they are they have been used to dentinite bombs.  

I'm no expert on any of this, but they "might" be on about you got a number before the government required registration.  Seem to recall a deadline a few years ago, wherein existing phone number/users had to formally register with the service provider.  May well have been in the wake of the Erawan bombing Lopburi3 eluded to above ^. 

To avoid excess data charges when using DTAC, apply Go Plearn. It is an always on 64 kbps data package that costs 30 baht to apply.

That way, you only pay for data when you apply a data package. if you don't purchase a data package, it will default to the 64 kbps package(which is actually good enough for text chat).

 

*103*55*9# and then press the Dial key.