I just got Truemove H a month ago, the iPhone SIM cart and I am using it in an unlocked Galaxy Note 2.

It has been working fine until last week when some of the numbers I have been texting/calling previously, I can no longer send a SMS to.

It just bounces back and says it had an error. I even tried the SIM in my blackberry 9520 and it wont send to the same particular numbers as well.

Any ideas?

So you could send SMSes to these numbers, and then last week you could not send SMSes to these numbers?

And you can send SMSes now to other numbers, but just not some subset?

Is that correct?

Are these numbers in Thailand? What service provider are these numbers on? What does the error message say, exactly?

I assume you have a remaining pre-paid balance and validity? #123# Send,

Sorry about that I shoukd have added more detail.

There are basically 2 Thai numbers(in the same city), which I have been able to SMS last week.

This week they have been bouncing SMS but I keep getting charged for the attempted send.

I just topped up yesterday woth 300 baht so it has credit and I also have a SMS pack which has not been all used yet.

The error says delivery failed. On my bb it says protocol stack error

So you can send SMSes to other numbers successfully? This is obviously vital to understand.

Do you know which providers these other people use?

You have checked with the recipients to make sure their phones are turned on?

If you cannot send, or receive SMSes, it could be a problem with the SMSC configuration.

Has anything changed recently?

I assume you have a TrueMove H signal?

I have TrueMove H, I can send SMSes.

Earlier this week I was SMS'ing a friend from my TrueMove-H plan on my iPhone 4. Suddenly, it stopped being able to send SMS's to that number. It would say "Not Delivered" with a white exclamation mark in a red circle. Clicking on the red circle: "Your message was not sent. Tap "Try Again" to send this messsage." Tapped "Try Again" with same results. I just gave up after four tries. Sent an e-mail instead. This was on 01-Sept-2013. I just chalked it up as "one of those things," but it seems to parallel the OP's experience.