BPL Mobile — Unauthorised change of caller tune

I am deeply disturbed by the companies high handedness in changing my caller tune to some trash song with out my knowledge and charging me for the same. I prefer the normal ring. Two months back
too they had put a song as my caller tune and charged me for the same. I complained and they removed
the caller tune but they said we can't refund the 30 rupees. Again theyt have done the same thing. I really wanty to take some serious action against this theivery.