Use the Microsoft Dynamics CRM 4.0 (2007) Endpoint in Crm 2011

Microsoft Dynamics CRM 2011 and Microsoft Dynamics CRM Online provide a backward compatible endpoint that lets you continue to use code that was developed for Microsoft Dynamics CRM 4.0.

http:///MSCrmServices/2007/CrmService.asmx

Ref:
http://msdn.microsoft.com/en-us/library/gg334316.aspx