Error 0

I'm fairly new to T-mobike and I've had the EXACT same issue twice this week while traveling in Vietnam. I have a brand new Samsung S22 Ultra purchased from T-mobile when I started my service 2 months ago. I've been traveling out of the country for the last 6 weeks without any issue until now. ONLY my text messages are failing with ERROR 0 message. I did try using a different texting APP with the same result. Data, calls and internet work perfectly on or off wifi but, I've never been able to send a text message on wifi only with this new phone and I think that in itself is a little strange. I've checked all my settings and reset the phone and APP multiple times with no change. My text messages didn't work for 2 days and I tried all the things customer service suggested with no change as well. They thought maybe I just needed to connect to a different tower in a different area but, that didn't change anything either. Then magically it  started working again after 2 days only to stop one day working AGAIN 1 later today. FYI My GF is traveling with me and has an IPhone 13 Pro. She has not had any issues with her service or text messages! 🤬🤬🤬 Any help or advise would be greatly appreciated as I use this phone daily for personal and business messaging.