duplicate notifications for windows 8 app

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C#

WinRT

we developed one app and implemented toast notifications. App is able to receive the notifications and am able to send notifications to the devices. but due to lack of unique device GUID, for single user am getting two channel urls. so single user is getting multiple notifications (duplicate). So if we have a unique id my problem will be solved.
suggest any ideas.
I have gone through this link also.

and the function I am using to get the device guid is

var token=Windows.System.Profile.HardwareIdentification.GetPackageSpecificToken(null);
var id=token.id; 

from this I am generating the guid.
drawback with this function is it will give different GUID's
if hardware components changes.