AirG unauthorized services and charges on my bill Vancouver, BC, Canada Internet

I have a Verizon prepaid phone that is only used once every other month.  I opened up last months bill and saw several charges for a "Premium SMS" service during a time period when the phone was off.  I called verizon and the charges come from a company called AirG. Apparently AirG send me several text messages saying that if I did not reply and opt-out, then I would be subscribing to their services.  First off, if I did receive such an text, I would have deleted it immediately as spam.

Second, everyone should know not to reply to such text anyway because of scammers and spam list.  My last bill had over $40 in unauthorized charges.  The Verizon customer service said they could not do anything because I did not take action to "opt-out".  I tried explaining that I never authorized any services and beside, how could I choose to opt-out if my phone has been off. But apparently this company has to power to simply charge people at will.  Such a ripe off. A complete scam of a company.