I unable to use Set-TextMessagingAccount in exchange 2010, tried both in sp2 and sp3 getting following error:

"

The operation couldn't be performed because object 'Aditya' couldn't be found on 'ex02.mydomain.com'.
    + CategoryInfo          : NotSpecified: (0:Int32) [Set-TextMessagingAccount], ManagementObjectNotFoundException
    + FullyQualifiedErrorId : C6F712B7,Microsoft.Exchange.Management.StoreTasks.SetTextMessagingAccount"

Athoght i am able to use "Get-TextMessagingAccount Aditya" successfully with following output

RunspaceId                      : e57177d4-6bb2-450d-acce-d56e81df6a9b
Identity                        : mydomain/Users/Aditya Mendiratta
CountryRegionId                 :
MobileOperatorId                : -1
NotificationPhoneNumber         :
NotificationPhoneNumberVerified : False
EasEnabled                      : False
EasPhoneNumber                  :
MailboxOwnerId                  : mydomain/Users/Aditya Mendiratta
IsValid                         : True

Please suggest