AddAddresseeL leave with KErrNotSupported

If I read SMS message, I can not create a new message using the following code, because the AddAddresseeL() leaves with KErrNotSupported. But I can create a new SMS message without  reading SMS message. What's wrong with it? Do I need two CSmsClientMtm for read and write SMS? Please help me, thanks.

    {
        // Set SMS parameters
    TMsvEntry indexEntry;
    indexEntry.iDate.HomeTime();
    indexEntry.SetInPreparation(ETrue);
   // This is an SMS message
    indexEntry.iMtm = KUidMsgTypeSMS;
    indexEntry.iType = KUidMsvMessageEntry;
   //Gets the ID of the current SMS service.
    indexEntry.iServiceId = iSmsMtm->ServiceId();
   
        // Create entry to drafts
    iSmsMtm->SwitchCurrentEntryL(KMsvDraftEntryId);

   // Creates a new child entry owned by the context synchronously.
    iSmsMtm->Entry().CreateL(indexEntry);

        // Set the MTM's active context to the new message
    iSmsId = indexEntry.Id();
    iSmsMtm->SwitchCurrentEntryL(iSmsId);

        // Add message body. Body is set twice because index entry keeps a copy
   // of some summary information. Index entry and full stored entry
   // must be in sync.
    CRichText& body = iSmsMtm->Body();
    body.Reset();
    body.InsertL(0, aMessage);
    indexEntry.iDescription.Set(aMessage);

        // Add destination address (recipient). Copy address also to the index entry
    if( iSmsMtm->AddresseeList().Count() > 0 )
    {
        CAknInformationNote* informationNote = new (ELeave)CAknInformationNote;
        informationNote->ExecuteLD(_L("大于0"));
    }
    iSmsMtm->AddAddresseeL(aAddress);
    indexEntry.iDetails.Set(aAddress);

        // Commit changes because index entry is only a local variable
    iSmsMtm->Entry().ChangeL(indexEntry);

        // Save full message data to the store
    iSmsMtm->SaveMessageL();
    }