If you go into your NTA settings you should be able to uncheck interfaces you don't want any netflow from. If you're seeing more than the one interface you want it's because you're either getting netflow from it (with 'accept netflow on unmanaged interfaces' enabled) or the interface is selected as a netflow source in the NTA settings.
mrxinu is right. In your case you should do this:
- Disable "Automatic addition of NetFlow sources" option under Admin settings
- Enable "Allow monitoring of flows from unmanaged interface"
- Manually check which sources to enable/disable using Manage NetFlow Sources.