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