You can cancel a merge to disconnect a mail merge publication from its data source.
Cancel a merge
You can cancel a merge to disconnect a mail merge publication or a catalog merge template from its data source.
Click Mailings tab > Select Recipients, and then click Cancel Merge.
When asked if you want to cancel the merge, click Yes.
Note: If you cancel a mail merge, fields other than Address Fields, Greeting Lines, and Address Blocks are converted to regular text.