Goodmorning @vivekkr0611 

You wrote that you have signal issues 90% of the time. When you are on the road / and or not at home do you have a better signal then? Can you swap your sim into your wife's phone and see if you have signal then? If you encounter no issues, then it could relate to an issue with your phone, but let’s not jump into conclusions yet. 

I’m looking forward to your answer. 

hey, @vivekkr0611 

A question from my side.
With your 8 pro (android 11?), would you go to settings > wifi and network > sim and network > preferred network type and see if it is on 2G/3G/4G/5G (automatic)?

If it's not too much to ask also go straight to Sim 1 (if that's where your t-mobile sim card is) and see if VoLTE and calling via WiFI are enabled?
(Sometimes you can use the above options to call in places where there is less coverage and / or if there is wifi available)

Of course, have you already rebooted the phone?

You can in extreme cases also reset the setting of the mobile data, calling, wifi and so on, this can be done (in android 11) settings > system > reset options > Wifi, mobile and bluetooth reset.

The above translated with a translator.

Good afternoon @Seccie , @Maarten098 . 

Thakns for the suggestions . I will try these options and inform the conclusion later in evening. 

Thank you for your answer @vivekkr0611 

I am curious to see if it had any effect :)
And thanks in advance for the feedback.

First I would also advise to try the tip from Seccie to rule out t-mobile.
Good luck with it!