Do you want to change the prefix of numbers in your contact list? See example: Number: 0980000030 Old Prefix: 0, New Prefix: +84 => New number: +84980000030
Number: +84980000030 Old Prefix: +84, New Prefix: 0 => New number: 0980000030
Number: 0980000030 Old Prefix: (Empty), New Prefix: +84 => New number: +840980000030