Can't Get Rid of the Charge

I am being charged $9.99 monthly on my phone bill for ringtone service that I do not use (never have). I don't know how or when it started. I called the number listed on their website, emailed their customer service, and texted "Stop" as instructed in a text that I received. About 2 minutes after I texted, I received another text from them alerting me that I can use some new ringtones. I just want to get rid of the charges, and seem to be getting nowhere. Help!