idea cheating with me by giving wrong information

my idea gsm no 7501515245
they offered me free caller tune. 0rs renewal charge
but after one month they deducted rs30 .
immediately I contacted customer care they said sorry for misunderstanding the balance has been deducted for renewal charge.
I’ve there free ct offer SMS till now.
They always say one thing in offer but after deduction of balance they always say sorry balance can not be refunded.