I git T-Mobile Unlocked Oneplus Nord N200 from Ebay.
Apparently you have to send to code to oneplus and have to wait 7 days. Way to bypass is convert it to non OEM version and then unlock it. Ref: https://xdaforums.com/t/convert-a-nord-n200-t-moble-metro-de2118-with-locked-bootloader-to-a-u-s-unlocked-version-de2117-in-400-seconds-with-modified-msm-tool.4631587/
- Going through the original guide for doing the process.
https://droidwin.com/convert-oneplus-t-mobile-metro-to-global-on-locked-bootloader/
- Download the MSM tool: https://community.oneplus.com/thread/1541327