The problem that you are facing is because of the double quotes. You have to escape the double quotes with another double quote that will help.
aws dynamodb put-item --table-name PhoneBook --item "{""PhoneNo"":{""S"",""12345""},""Name"":{""S"",""abc""}}" --return-consumed-capacity TOTAL
You will get the output as follows:
{
"ConsumedCapacity": {
"TableName": "PhoneBook",
"CapacityUnits": 1.0
}
}