Actually, I created File Drop automation to import data into Data Extension. I dropped different files into the same file location. After the completion of automation flow - it imports data of the previous file again or sample set file data imports again. I have no idea what's happening! Anyone face this kind of issue.
Use the date variables in your file name. I.e.:
Your file name would then be named “filename_04132019.csv”
In the import activity settings there are two options you can choose:
- Skip import if last import was less than [x] hours Fail import if file is older than [x] hours.
- Allow System Buffer of  hours
The system will pick up the latest file and depending on your settings, will skip or fail imports if it doesn’t meet the criteria.