At a guess, calling your SP the same name as a column in your table might be a problem: I'd give the SP a more sensible name ("GetEmployeesByJob" maybe) and probably rename the column as well, if it does contain a row ID value. My standard for ID columns is to call them ID and specify the table name when I use it and there might be confusion:
SELECT c.Name, o.OrganisationName
FROM Clients c
JOIN Organisations o
ON c.OrgID = o.ID