Poor internet in dual sim compared to when non mobile network sim is turned off

[pdev]

Samsung M21- There is very much issue in internet connection when both sim are turned on while there is lot of improvement and stability when only mobile network sim is enabled. Mobile internet sim is already placed in slot 1 and it shows 4G still internet is low when second is also turned on. Signal strength in both of the sim is around -80,-85 dBm. What can be done to solve this issue? One cannot always turn off the second sim 

[Suryansh112]

Turn second sim to 2g only mode

[Suryansh112]

And one to 4g

[Fai_Xan]

yes same problem in my m21
But i have used 2 jio sims
and i turned sim 2 off some times but no improvement seen...😭😭😭

[Samsung_Support2]

Dear Samsung Member,

Greetings from Samsung Customer Support!

To resolve your device network issue please visit this link: https://www.samsung.com/in/support/mobile-devices/samsung-mobile-network-issues/#:~:text=1%20Check%2....

For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).

Thank you for writing to Samsung.

Warm Regards,
Samsung Customer Support

[pdev]

Samsung Members application is not applicable for Samsung M21 and the link didn't helped at all. Can anything else be done? Is this issue covered in the warranty period?