Hello again, I'm here to update the situation if someone end up in this same situation please don't the mistakes I did,,
After I try everything in the end I find out my phone was not rooted and the problem is with OnePlus 6T Android 11 finally update, and I didn't find any fix because as far I know there is no official fix released,
But because of all this I end deciding to roll back my device to Android 9 which is build in version of one pluse at least it was for me when I bought it,
But this is where I mad a mistake and I almost end up getting into big trouble but I'm sure it won't be issue for many people here since mostly people have PC,
So after I try to downgrade my device I end up installing the wrong version of build in Android version, and by wrong version I mean is that if u going to downgrade your device u must have to know what is your device full name in my case it's OnePlus 6T A6030 and u must have to install the same version of rollback to your device or otherwise you will be stuck with a brick phone showing error ""Build version and HW version are not match""
But it's still fixable only if u have PC and some tools which are extremely expansive where I live,,
I don't have a PC so it became a very big issue to me and I had to rely on the market which basically fix these kind of things, but the problem is that many of these guys don't even know what they are doing and because of that they end up causing more damage then fix it,,
I had to go through floor after floors and after leaving my device in the hand of so many guys I finally able to find one guy in the market who actually knew why this error is there,
If I just gave my phone to first guy or any others then I'm sure I won't be writing this since my phone would be dead after being exprimented by some idiot who call them self softwhere engineer,,
Any way after this guy told me why I'm seeing this error I finally felt relief and ask him to fix my device and which he did!!
I can't say how much this mad me happy since buying a phone like this in my country was just way ahead of normal working class guy like me , but what is the most strangest thing is that this guy who fix my phone actually also didn't know much either, after my device is on I find out now my device is T-Mobile and also it's only single sim, I used duol sim before but now I can't and also my device is full of stupid T-Mobile apps,
I ask him what's this and he had no idea and he didn't even believe me when I said my device is not T-Mobile, I'm sure he just only learn to fix this issue by watching YouTube videos and doing expremints on customers device, which is a very common thing here,,
So after all that now I end up with T-Mobile version of build or whatever it is called inside my phone and also it's not Android 9 but it's Android 10 and also showing me update notifications,,
And of course I'm toattly find with T-Mobile version and I will also ignored the update since I wanted my phone to be fix and its fix now,,,
I hope this might help anyone who is new like me and don't own PC or laptop, and don't make the same mistakes I did,
And I know the error I got it's not a very big issue but again not having PC make it a huge a problem because they people who tell you they can fix this in the market also ask ur permission to work on ur device and there is chance your device will be fix or it will be dead so they will ask for ur approval to fck up ur device,,
I'm from Pakistan and this is how it is here so please don't give ur device to any market guy who doesn't know shit,, do ur own research and then ask all the question to the guy before giving ur hard earn phone,,,
And thank you everyone here for answering me and guiding me and please ur welcome it correct me about anything I said if I'm wrong about anything and make it easier for others to understand, and I would also love to know what is this T-Mobile thing happning to me and how is this even possible,,