Uploading Into Dialer Doesn't Replace Info

When uploading data from a list of previously called leads, we wanted to update one of our custom fields (service type) from plumbing to electrical - however, when uploading the records, and selecting the appropriate fields in the .csv file, the information in the system still has "plumbing" as service type rather than the replacement "electrical". 

A simple warning about the information will overwrite previous data in the selected fields will alert people so data isn't accidentally overwritten that wasn't meant to be.