As I understand it you made the change on the Swiss webpage?
If correct it is unlikely that ticket has been reissued. LX can't do it because it is an award ticket issued by LM and most likely LM has no knowledge of the changes to the reservation you made with LX.
If the ticket No. you see after the change remains the same, you need to contact LM for reissue of the ticket. You can't travel on the original ticket when the flights have been changed, the ticket needs to be reissued. If the ticket No. has changed after you made the change, the ticket has been reissued and you should be good to go and there is no reason to contact LM.