Samsung Note 10 plus no 3G connection

Kindly I have this issue with my Note 10 plus quite a while and trying to fix it, but sadly still did not find the solution. After having N975F/DS for a year, when the phone goes to 3g network it loses the signal and gives a message no network connection. as a result, to receive calls and sms I need to stay in 2g only mode, and the data I use a wifi connection, but cannot use lte as if I got a call the phone will go to 3g, resulting unreachable message to the caller. I started to search the internet for a solution and after a long search I have concluded that I need to flush the device. I have downloaded the latest version from "sammobile" and as the country that I live in does not exist I have used the closest country. An hour ago I have finished flushing the rom of the device using odin and after getting back the phone to work, tried from auto mode (4g/3g/2g) mode to make a call, from 4g it went to 3g and the shock, same issue cannot connect to the 3g network. I have tried the sim card in another phone and it worked smoothly with no issues, and as well I have tried another sim card from a normally working phone in this phone and the issue exists. Kindly I need help.