You can override specific text in language file, without even touching the language file.
In case you want to override specific text in language file, then if you change text in the existing file, then it will overwrite the existing one for sometimes only because on up-gradation or re-installation of PayPlans, changes made by you won't be retained. So as a solution, PayPlans allows you to make another language override file with the name en-GB.com_payplans_override.ini file which will not be touched on up-gradation.
Front End Language Files : ROOT // languages // en-GB // en-GB.com_payplans_override.ini
Admin Language Files : ROOT // administrator // languages // en-GB // en-GB.com_payplans_override.ini
Let's take an example of editing text in front-end language file of PayPlans.

This way any text can be edited through override concept. Above example shows you how to edit text of front-end language file.
In a similar way, you can edit PayPlans admin language also by creating language override file at ROOT // administrator // languages // en-GB // en-GB.com_payplans_override.ini. Copy strings which you want to change from ROOT // administrator // languages // en-GB // en-GB.com_payplans.ini and paste in the created override file.
Using this concept, your changes in language file will never be lost on upgrading PayPlans.