Overcharging customer and ripping them off

DSTV is paid in advance. I paid R699 27/01/2016 for February16(15days viewing). On the 5/05/2016 I paid R149.00 for the Explorer which was delivered on the 10/02/2016 and installed. On the same day my DSTV compact was cancelled, which mean there should have been a credit for the month of February 16.On the 27/02/2016 I was debited with R824.00 which I assumed was for the explorer which is price Lock at R899 for March 2016. It was suppose to be R899 - R149 which was paid in advance =R750.00. Great is my surprise that on the 29/03/2016 I was debited with R1025 for April 2016 subscription which is to be price lock at R899.00. Now I am being informed when I cancel one package in the middle of the month it does not cancel the subscription(old one). How can you be charged for two packages. DSTV is ripping people off and the call centre with there supervisors don't know what they are doing. I want the access money back in my account as I only subscribe for R899 and not R1025.00 a month.