SQL substring query help?

I have a bit of a problem trying to query a substring. I'm needing to split a ContactName(which I've done) and query the last name part of it. I would like to be able to query it if a person only enters part of the last name (say the user enters an S - it would receive all last names starting with S, OR maybe enter it as Smi - and the query would return Smith and Smithers) is that possible? I currently have a non working query for my last name and this is what I have so far. This is in C#, but I'm using a sqldataadapter.

SqlDataAdapter("select o.OrderID, c.CompanyName, left(c.ContactName, CHARINDEX(' ', c.ContactName)) as Firstname,substring(c.ContactName, CHARINDEX(' ', c.ContactName)+1, len(c.ContactName)-(CHARINDEX(' ', c.ContactName)-1)) as Lastname, o.OrderDate, o.ShippedDate FROM Customers c JOIN Orders o ON c.CustomerID =o.CustomerID WHERE SUBSTRING(c.ContactName,2,10) = @lastNameFilter ORDER BY c.CompanyName ASC", connection);