Changing frequency on RF Link
In the 433 MHz band, there are 69 channels and the list of them and their exact frequencies can be found here. 

As far as these modules are concerned, I can't see any mention of channels or exact frequency in the documentation. I know that some (for example this one) modules do mention their frequency, but so far I've been unable to actually find any modules whose frequency channel can be programmed. They do exist, though, since I've seen them in some products. 

Some manufacturers (can't find the link at the moment) mention that modules with channels other than default are available for order, but the downside of that is the fact that manufacturers usually do not want to talk to small buyers.