Did you try the "Replace Data Source" option, you can find that in the data tab or on right clicking the data sources. I guess that should work for you.
It sounds like you've bought in the data as a blended data source. If you have one orange tick and one blue tick, that means you've got a blend between these two data source.
To replace one with another, just right click on one of the data sources and select replace data source:
Select your current and then the replacement:
Then replace all references to update the new column: