Virgin Mobile — Regarding unwanted service

I have Virgin mobile service provider. on 15th of june i got a promotional call from virgin mobile and i heard it for 12secs and then cut the call. After wards i got a SMS saying that i have subscribed Devotional Pack and 7rs has been deducted. While i didnt accepted it. I complented about it to them but the way they told me to deactivate the service is not working. Even when i try to use that service i am unable to do so. Now they are deducting 7rs every week and refusing to pay me my money back. I had complented about it through mails even through customer care. But nothing is working out. Please tell me what should i do?