AlaskaLinuxUser's Scratchpad

Recently I ran into an odd problem: I could send MMS text messages from my phone, but not SMS text messages. Typically, when you have a problem, you can send SMS and not MMS, but this was the opposite. It took me several days to figure it out, so I thought I’d post the solution here in case I need it again, or perhaps to help others.

When it started, I thought I could actually send no text messages at all. It was odd, because I was still receiving text messages, just couldn’t send any. Then, in my efforts to try sending a message, I sent a picture to my wife, which went through. Then I realized with more testing that MMS (multimedia) messages could go through, just not SMS (plain text) messages could not.

By the way, as a side note, to force SMS messages to be sent as MMS messages, you can do three things:

1. Add a subject to the message (if your app permits you to).
2. Add a picture to your message (I did this for a little while with a white square that was really tiny).
3. Use an app that forces sending SMS as MMS messages. (YAATA texting app was the only one I found that did this.)

While the above worked to force MMS and send my text messages, the problem still wasn’t resolved, so I kept at trying to fix it. I went through all of my APN settings, contacting my carrier and double checking them. That didn’t fix it. Then I reset my network connections in Android from the settings menu. That didn’t fix it. Finally I tried flashing my phone back to stock and that didn’t fix it!

But then I realized something. If I put the sim card in another phone, it still didn’t work. It wasn’t my phone, it was something with the sim card or setup on my carrier’s end.

It is really difficult talking to my carrier’s tech support. They don’t really seem to know anything at the normal “entry” level tech support that you call. It is some poor soul who is getting paid minimum wage to read a script that tells you to do all the things I already did. In the end, tech support didn’t solve my problem, because they didn’t know what it was.

However, I was still determined to keep trying, I mean, what else could I do? That’s when I started doing comparisons between my phone and my wife’s phone. That’s when I finally found the problem. Turns out I had a bad SMSC number in my sim card settings. I am not an expert, nor super knowledgeable about this, but this SMSC number seemed to be something that is read from the sim card and traveled with the card to each phone I put it in. Here’s what I found online about it:

To communicate with the other nodes in the SS7 network, each node requires an address known as a global title (GT). For example, the nodes can be HLR, GGSN, SMSC etc. Smsc or message service centre number is the Global title/Address of SMSC. It is also known as a message centre number, located in HPLMN of a mobile network operator. A mobile operator uses SMSC for providing SMS services to subscribers. The number is an E.164 type of number. Similar to any other mobile global title, it has digits along with other information. Sim card stores the message service centre number.

https://www.cspsprotocol.com/what-is-smsc-number/

So, it would appear that this number is supposed to be given to you by the carrier, and it is stored on the sim card. Now, the above quoted website does have instructions on how to change it, but that didn’t work on my phone. How mine got messed up, I’ll never know, but it did. How you are supposed to know what the number is, and get it from your carrier, I’m not sure, because the regular help desk people seem to know less than me about this number. However, here is how I fixed it on my Android 11 phone:

1. Open your dialer, dial *#*#4636#*#* (This will take you to a special menu)
2. In the special menu, select Phone Information at the top.
3. Scroll down to the bottom till you see SMSC. Select Refresh.
4. It will populate the SMSC line, in my case it said +7, but my wife’s phone had a different number, a much bigger number.
5. Put in the proper SMSC number and press Update. (I used my wife’s.)
6. Text someone to see if it works.

At first I was concerned that my wife’s SMSC number might be unique to her, but it does not appear to be. It looks like a 10 digit phone number. I guess it is the “number” your phone “sends” your text messages to be actually routed to who needs it, which makes sense to me. So it looks like if you have this problem, you can get the number from anyone in your local area who has the same carrier as you, I think.

Either way, I praise God that I have text messages working normally again.

Linux – keep it simple.