In the past i have used the SFTP (secure FTP) Marketplace module to do the use case that you are seeking.
In the documentation you can see that once you add their configuration pages which lets you configure your SFTP Server. Once that is done, you can use their SFTPConfiguration_GetDocument microflow to pull any file from the SFTP Server.
But these Marketplace modules are tailor made for downloading the file directly and not to process them.
So you have to tweak their Java actions to not download (Content Disposition Mime Type flush to the Stream i think) but to transform the downloaded stream to a FileDocument entity and then call a microflow in which you can then call your ExcelImporter Microflow to parse the data as per your template.
I know this is a kind of a TLDR; but very well possible.
Let m know how it went :) Good luck