Sales Person

Team - Got a question on the whole Sales person and Customer Contacts. Can you please help me?

Used manage users screen to give sales person role to a user. Then used manage resources screen to add the Ref Data Set for that user who is a salesperson.Then created order and added two different sales person and then imported in AR and both sales reps show up in the sales credit option. Can we have a sales person as a default sales person for a customer ? Is there a way in customer screen where I can associate a sales rep/person ? Or just need to use the contact screen.my client also has some other