Phone verification code

I need to add my postpaid mobile number to my battle net account. When I try to add my postpaid number I don’t receive the security code. I tried every troubleshooting guide you guys have, but no luck. I even tried my service provider and they mentioned there are no issues from their side. My account region was previously set to Russia but now I changed it to Sri Lanka since I live there. Originally my account didn’t have a mobile number and the number I’m trying to add is not used for a different account. I even bought games like MW 2019 and Vanguard using this account. I saw people talking about this mobile number issue in the Warzone community. One of my friends fixed this issue by contacting customer support. I can’t play warzone because of this. I hope you guys will be able to help me fix this issue.

I’m Also from sri lanka and facing same issue. need a solution for this