Have unauthorized charge on my credit card

After returning the last 2 shipments from this company they will not return my money and continue to bill me for $49.98 a month.  I asked them to stop this in May 2013, but the charges are still coming in.  When I wanted to escalate, there was no manager or supervisor available.  They also claim not to have a phone number to their main headquarters, who supposedly are the only ones with authority to grant a refund  They also supposedly don't use internal numbers to track complaints.  I spoke to Carla and she gave the number: 13637568 after spending over a half hour on the phone with her.