not familiar with the term “service user” in terms of LDAP, but if you mean you need an account with search privileges to log in to perform the lookup before attempting the bind with the end user, yes, wpDirAuth supports this. In the wpDirAuth settings it is referred to as Bind DN:
Enter a valid user account/DN to pre-bind with if your LDAP server does not allow anonymous profile searches, or requires a user with specific privileges to search.