NOT GETTING WHAT I PAID FOR

We pay our DSTV subscriptions on an annual basis. We pay in mid April - deal is you pay for 11 months and get 1 months free. Our next payment is due on 14 April 2018. I receive an SMS today notifying me the account is overdue and I need to pay R825.45 today to avoid being disconnected. I phoned the call centre to be told that due to the fact we upgraded to an explora decoder this deal no longer app****. I asked to speak to a supervisor and was told to hold. I've been holding for 21:44 minutes listening to Sam Smith but no supervisor! Can someone explain to me how is it that because we upgraded our decoder, the 1 free month falls away! my user number is ********** 5