Indeed you have to commit the changes to the Entity and Exit the editing mode, before calling SubmitChanges.
Please check this out and let us know if you have any additional questions.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items