7726 Spells spam...7727 does not.  I have seen outgoing texts with notation it was a pic being sent out and incoming from 7727 and outgoing to 7727.  This is NOT a text reported as junk.  I am pretty sure it is a messaging app to keep the numbers from being seen on the usage details of the bill.  

What makes you say that is a messaging app? I cannot find a consistent thing about the number 

Did you find out anything about this?

I have been getting the same thing showing on the app for me. I do not have any secret apps, as the person below recommended may be the issue.

I called T-Mobile and they put in a ticket, said it doesn’t show on my actual statement or records, only shows on app. 

I was very concerned about that 7727 number. Since it show pic coming out and txt never coming in. But after doing Long research, I also check my other two line my daughter and my self, there were also txt coming in and out to that number. I am an 100% sure I didn’t send txt. So to those saying it’s an app be sure it not. Most be T-mobile system. Which always broken. The same with iMessages not showing in the app only in the phone. 

It could be a short code enabling pass through. 7727 on the dial pad is pass.

What does that mean? Lol

Google Tmobile short codes and it may give you a more detailed answer

Okay so the reason for the 7727 text happens when you delete a message and report it as junk! It sends a report to t-mobile and Apple. Not sure how no one was able to figure that out, BUT THAT IS THE ANSWER!

7277 or 7727?  7726 spells SPAM and is used to report SPAM texts.