OnePlus 6T was officially launched in the U.S. previous year with the T-Mobile branded OnePlus 6T. All the features of the device were the same as to that of the international variant, but with a few minor difference in the sim card tray. The T-Mobile OnePlus 6T has a single SIM nano-card slot. But, one thing was that there was a lack of immediate bootloader unlock option. How this worked was the customers who bought the T-Mobile version of the OnePlus 6T, needed to pay-off the price of the device completely and get the SIM-unlocked before they could go ahead to unlock the bootloader of the device.
Moreover, this process took at least about 40 days for completion. However, there is some good news for the T-Mobile OnePlus 7 Pro users as there is a workaround for unlocking the bootloader and skipping that 40 days of time for unlocking the bootloader following the official procedure. Thanks to XDA Member, Daniel Marchena, discovered this method of unlocking the bootloader, even if you do not qualify for the official unlocking procedure. Moreover, this method is pretty easy and of your follow the below-mentioned steps correctly, then you will be able to skip the waiting time and get your T-Mobile OnePlus 7 Pro unlocked.

NOTE: This is likely a limited-time opportunity and this procedure might get blocked. The process depends on flashing OnePlus’ Android Q DP3, and OnePlus will likely patch this method.
Steps to Root the T-Mobile OnePlus 7 Pro
Please note that this procedure of rooting the OnePlus 7 Pro will completely erase the data on your device. So, make sure to make a backup of the device memory before heading ahead with the process.
Step 1:
Thanks to XDA Senior member, slayerh4x for this flash procedure. Firstly you need to flash the international firmware for the OnePlus 7 Pro. Follow the below steps to accomplish that;