When your channel list is how you want it in your receiver, load your channel list (lamedb) into an editor called Dreamset.
(Remember to do all of the following for TV, Radio and Data if you want to)
Right-click on the channels and 'select all'.
Right-click on the channels and go to 'set service(s) attribute' and choose 'yes' on 'untouched by SDT'.
Obviously, save the lamedb and send the channel list back to the receiver.
I think you have to restart Enigma2 for the changes to take effect.
If you later want to re-scan normally or let the receiver update the list automatically, perform the above process again first but choose 'no' on 'untouched by SDT'.