hello, i'm trying to sms a friend, few days ago, it went through and i got a response, but today i am getting "card 1, error 38" ; does their phone have to be turned on to get SMS messages, or would the error code tell me if they were or weren't blocking my SMS?

another time to another number i get "card 1, error 21"

my provider is DTAC, is there a list of error codes meanings?

Mu usual not so inventive first step: ask G

card 1, error 21

card 1, error 38

SMS error 21

SMS error 38

etc,

At least you are not alone and probably not DTAC specific.

I browsed through some sites but not found the one shot solution in an instant.

What phone are you using?

i tried G, no luck.

Nexus 5 , US version

in general, is it simple to block SMS from unwanted people?

Do you get error messages when sending to local Thai numbers?

'Card 1' sounds like it's referring to your SIM Card position

CMS ERROR's (GSM Network related codes)

CMS ERROR: 21 Short message transfer rejected

CMS ERROR: 38 Network out of order

It's possible that the 'tower' you were on is misconfigured, as that sender number worked for you before.

Some help forums suggest the issue may be with the phone and recommend removing then reseating the phone battery, power back up and try again -- sometimes a 'state' change occurs that gets cleared when you remove the battery.