Unauthorised double debit on my account

My account was double debited in January and I have been sending email upon email to these people, trying to resolve the issue. I renewed my service with Beame and Mix Telematics last year. There is NO reason as to why my account should have been double debited! Nobody has rep**** to any of the emails I have sent. Nobody has called me back yet when I enquired about renewing my service I received a call the same day within a couple of hours. The after sales service is clearly below par. I have never experienced such a lack of concern from one of my service providers before especially when it comes to an UNAUTHORISED debit on my account!