Which one do you think is more important, selling service or after selling service or the complete each other?

Both service during the selling process and after sales service are equally important. This is a way of making customers come back to you 

Both are most important parts in selling  and service while you are on deal, service that you porvide is more important than sell because your  service will bring back the coustomers which is more important to the organization satisfaction?

they complete each other,although after sales service strengthens mutual trust with the customer

It should be complete each other.By that you can maintain a good relationship with the existing customer and meanwhile you can seek for new customers two.It's like a coin of both sides.