Vivint Smart Home, aka Vivint, APX, Blackstone Group Cancelled my account in June 2016, still being charged monthly bills Provo, Utah Arizona

I cancelled my account for my home security when I moved back in June 2016.  I have been continuously charged monthly bills since.  I have called numerous times, and every time I’m told that the cancellation is “Pending” and that they have to email the department responsible for reviewing such accounts.  It’s been months and still no response.  I’m being charged $49.99 a month and we have incurred $136 in insufficient funds fees because of the illegitimate charges.  Every time I call, I’m told that they have emailed the “department”, when I ask to speak to that department I’m told that they don’t accept phone calls and that is the best that they can do.  Meanwhile I’m still being charged.  I called again today and for the first time I’m told that the cancellation notification must be written.  After I’ve called numerous times this is the first time I’m being told this????!!!!  I expect a full refund for all charges including the fees incurred from those charges.