Under the All apps the true caller is shown twice by the play store / Under the settings there is only one app not two. (click images for larger variants)
Android Version:4.1.2 Jellybean
Device: Samsung Trend Duos.
In the above image the True Caller application is shown twice and both are of the same no extra app on(or plugin for that particular app). I have force closed the application ,later switched the device waited for some time and restarted the device and still the application duplicate is displayed under My apps.
There are not two apps as you can see in the downloads section.(The applications list is sorted name wise so there's no chance of missing a second true caller app)