how to count distinct record with mulitple different fields in Oracle 12

I have several records below in ORACLE 12. Basically, there are two Rep persons that sold their products to six different customers. I would like my result to show all six different customers but only count the Rep_Id column as only two distinct persons.

 Rep_Id Sale_Dt    Customer_Ref
    30255   10/8/16    65839
    30255   10/8/16    52059        
    30255   10/8/16    52035
    30256   10/10/16   53253
    30256   10/10/16   53533
    30256   10/10/16   53564

Here is what I was trying to do and my result has 6 Reps instead of only 2 Reps as from above. Any pointer would greatly appreciated.

select
Sale_Dt,
Customer_Ref,
count(distinct Rep_id) as Persons
(
 Rep_Id Sale_Dt    Customer_Ref
30255   10/8/16    65839
30255   10/8/16    52059        
30255   10/8/16    52035
30256   10/10/16   53253
30256   10/10/16   53533
30256   10/10/16   53564
)x

Order by 1