change in Customer name and Address

Dear SAP Gurus

I m facing a probulem that when SAP endusers creat delivery and other billing docs. they change name of customer and their address ie. manupulate the things which is not a good SAP practice.

Suppose we make a sales order and we can delay its delivery to next month and at the same time there is a customer who need immidiate delivery so they use sales orders of different party and change the name and other details . Please guide me how to stop this practice.

Thanks in advance

Rajesh