You cannot disable or delete NaturallySpeaking commands such as
select <next phrase> because they are hardcoded into DNS. The only commands you can disable (exclusive to Ver. 10) are the Natural Language Commands for Microsoft Word, Excel, PowerPoint and WordPerfect. As a workaround, you can say
switch to Dictation Mode, but this will require switching back to normal mode in order to use commands.
In our opinion, the real solution would be to attack the root of the problem. If you could supply us with a little more information such as does this command seemingly go off on its own (recognition issue), command fails to work or only partially works etc... we might be able to offer additional assistance. Select-&-Say is an important part of NaturallySpeaking but there are a number of Select-&-Say problems that can easily be resolved if you can fill us in with more specifics. When it comes to forum questions, it's almost impossible to offer too much information.