Depends on the type of phone. Is it an iPhone?
Then you can use the iPhone Configuration Utility to create a profile and download it to your phone, which tells your phone not to automatically connect to the REMOTE network. I believe there are plenty hits on Google for that.
As for gwatpe's problem: you can disable DHCP for the REMOTE wifi network on an iPhone, and manually specify the same IP address and Subnetwork mask as you had before. Leave Router and Gateway empty, and you will be able to use mobile data for Internet, while connected to the REMOTE network.