Jio is providing free caller tune service and it does not cost. You can change it unlimited times and no validity issue.
You can choose your desired tunes using jio music app but in JIO Phone, there is not option to set, so below are some tricks to set it for your JIO Phone:-
Borrow someone Jio mobile for 2 minute
First you need to borrow your friend mobile and open jio music application in his mobile, set tune in his mobile which you want to set for your JIO Phone.
Now call to his mobile number and press * and now you get sms, so reply with yes.
Now you set your caller tune
This is copy trick. It is easiest way to set.