Something is going on with T-Mobile's HD Streaming on One Plus and One Plus International plan.
I switched from AT&T to T-Mobile today and chose One Plus plan for two lines. Later I tried streaming video from youtube. The video would start playing in low res(360p and lower), but once I switched to 1080p the video would stop. The signal strength and data speed is fantastic in my place, speedtest.net tests show 55-80 Mbps download and 14-21 Mbps upload. So this is clear evidence that video steaming is throttled on my One Plus lines.
So I called support and was told that HD streaming feature was already enabled with my One Plus plan. And I am supposed to be able to enable/disable it in my.t-mobile.com "Profile - Media Settings". But I went there and the "Media Settings" does not exist. After some efforts, the support managed to "fix" it. I am able to stream HD on my primary line now, but there is still no Media Settings in my profile and the other line still can't do it. So I made another call with the support but they were not able to fix the other line and had to escalate.
Later in the day I checked my account "Plan details" and I finally understand how the first support technician "fixed" it, I was given an HD Video Data Pass for 8 years on my primary line but not on the other line. Nice! Thank you T-mobile but this looks like a walk-around. One Plus is supposed to have HD streaming by default without HD Video data pass.
For folks who have the similar issue, this is 100% related to settings on T-mobile end. No amount of reset/backup/restore your device will fix it. I have the proof as after I switched SIM card between the two phones, the "bad" phone started to steam HD and the "good" phone could not streaming HD anymore. The streaming throttling is associated with the line(SIM card).
The same issue are reported on at least another two threads:
According to these threads, this issue has been going on for weeks, customers are paying for services they can not use.
T-Mobile, please have it fixed ASAP!