Can we still use the same data load if the flat file is changing?

Summary:

We currently have a flat file provided to us from a vendor. This flat file is loaded via a data load rule. We have the import format mapping defined based on the columns within the flat file. We are switching vendors and the flat file columns are changing. I tried to update the import format mapping to reference the new column numbers but it isn't picking it up. Does anyone know if that is normal functionality?

Content (please ensure you mask any confidential information):

Is best practice to create a new import format/data load rule?

Version (include the version you are using, if applicable):