I am having exact same issue with just one contact. 

We were just in t .obile store. I can send message to that number now using my existing contact. But, receive replies on the "sip" contact. The language in the "sip" contact makes it seemlike messages going through a PC. 

I am having the some problem, is there a fix for this problem?

Bump. Also having this issue with exactly ONE contact. This person uses Metro PCS. Just started within the last week or two.

Same! Been having this same issue with the same contact for about a year now. This person uses metro by tmobile as well.

Any answers???

What did they do to fix it?

They did nothing. They were at a loss. It is not fixed. 

Following. I lost the ability to text my son although he can text me and I have no problem texting anyone else. I get the same "phone number" in my contacts. T-mobile showed my how to test network connections and it worked for 3 messages then failed again. Let me know if anyone else has any ideas. 

Yep, yesterday two messages worked for me. Then failed, again.

im having the same issue...please resolve

I don’t know what’s going on but I can tell you that the SIP address looks like a long-ago backdoor to allow people to call T-Mobile phones from PCs and other Internet devices. It was closed down due to security concerns. I only found out about it a couple of weeks ago.

I saw PC in there and thought same....but messages that do go through are her phone to mine. It's very weird. 

I am having the same issue. It’s one contact, my husband. The people at the T-Mobile store had no idea what was going on. So no solution. I tried to delete and redo the contact, nothing helped. Oddly about 5 months ago my husband was having a problem texting me. It ended up resolving itself.

I have the same problem and it only one contact, my fiance. What is the solution? 

Same. It’s my mom. Anyone have an answer yet?

I'm having same problem.  It's with 1 contact.  Tmobile can't help? No solution?

Had the same issue with sip and only affecting 1 contact.  We did the system  update to Android 13 and she texted me and I responded and it worked.

It was the update that did this when updated a week ago. Do they have new update that fixes it? I have s22. 

I'm having the same issue. Why isnt this resolved yet?

I'm having the exact same problem with a couple of my contacts. Happened after the latest update. T-Mobile please fix your mistake!

I just started having this same issue with my Mom. This is clearly a common problem. Where is the fix T-Mobile?

I'm having the same problem with a new contact. She can text me, but I can not text her. Weird. Please fix