[otrs] Service/SLA For Everyone.

Hi I would like to implement the Service/SLA feature of OTRS for all the users. I don't have a customer database because we don't give access of customers interface to them. I want to implement this feature for everyone and not just for the emaill address which are in my customer database, how do I do it. I was searching the SysConfig but couldn't find any such option there. can someone point out this setting please. Thanks your support is apprechiated. Regards Misbah