You have to add a TableStyle for that to the grid, using the grid's properties.
Set the MappingName of the TableStyle you add to 'CustomerCollection', and add a gridcolumnstyle to your tablestyle. Set the mapping name of that gridcolumnstyle to ContactName and set the caption text to Contact Name
Watch the casing, it has to be correct.
REcompile and run, you'll see 1 column now.