SELECT MIN(dateTimeStamp), CUS.customerName, CUS.CustomerID

FROM EasyRecharge.dbo.CustomerUsage CUS

INNER JOIN EasyRecharge.dbo.Customers_Dormant CNU on CUS.FromMSISDN = CNU.MSISDN

WHERE ([DateTimeStamp]

between '2009/07/01 00:00:00' AND '2009/07/08 23:59:59')

GROUP BY CUS.customerName, CUS.customerID

This is assuming that the dateTimeStamp column is of dateTime datatype. You might have to do all of that formatting to this column but I think this is close to what you were asking.

Let me know if this works.