How can I uninstall this app which keeps getting reinstalled?
Sounds clearly a malware. In such case, there is always another app/scripts that reinstall it whenever you uninstall.

Download ES Explorer, open it.  Enable hidden files in its settings, also enabled root explorer.

Now navigate to the data folder, or even /system/app or system/priv-app and see if you can find some weird app names and look also for folders which names start with . (dot) and delete them.