it is correct saying the following about services?
<b>Service master</b> and service category <b>are only for buying services</b>. That means you can create service master for creating service order.
<b>Material Type DIEN</b> is only use to create service material, which <b>we are using to sale the services</b>.It is mainly for customer service.
It is mandatory managing customer services functionality with material type DIEN?