Earlier it was Rs 15 for 3 months and now its Rs. 7 per month for setting a callertune in Vodafone but now it can be done for free via this facebook app i.e. Rs 7 per month is now Rs. 0 per month
I have used this and it works as mentioned i.e. Rs 0 for setting the tune
Some 3-4 months back ago, the charges were as you mentioned i.e. Subscription charges Rs. 30 per month and Rs. 15 for selecting a song which is valid for 3 months (90 days) but now (I am from Chennai) they are charging Rs.10 per month for the subscription charge and Rs 7 per month for the song.
So earlier, for 3 months it was Rs 30 *3 = Rs. 90 (subscription charges) + Rs. 15 (song selection) = Rs 105, now its Rs 10*3 = Rs.30 (subscription charges) + Rs. 21 (Rs. 7 * 3 = song selection) = Rs.51
With this app, your song selection of 21 is saved so for callertunes for 3 months you pay only Rs. 30 (this is what is happening to me so far)