Please reset network setting of both Sim one by one and than reset all settings of your's device in general management settings also Flight ✈️ mode on n off one time,restart your's device without any Sim in slots, interchange Sim in slots, turn off power saving mode then try to it's again. If you like please accept as a solution it's help to others users also, click on 3dots in my reply section and click on accept solution. Thanks.
Search for a real technical person there. If you don't get an answer then record their behavior as proof and type complaint letter, mail it to CEO of Samsung in Korea, and all the chief members of Samsung...
In case the issue still occurs, please visit the service centre for a physical inspection of your device. You can locate your nearest service centre with this given link: https://www.samsung.com/in/support/service-center/
