Message delivery failed.
Recently , I changed my iPhone from iPhone 7 to iPhone Xs. But in iPhone Xs message delivery failed. for SMS, I am using Sim card of India and recently, I am in South Sudan Country. I have also tried with *#5005*7672# to change SMS center number but it shows error performing request Unknown error.
I have also checked ICCID number which is correct.
What is the problem I can not understand.
iPhone XS, iOS 14