DSTV account

In February / March 2016 I have a request to change from DSTV compact to DSTV easyview. The reason was due to the ridiculous price I pay for REPEATS. nevertheless it was downgraded. I was even billed accordingly. Then I was contacted a few days ago saying that I owe DSTV money. When I asked why because the proper amounts were debited and then I also made cash payment equivalent to the debit order payment which was R100. Now the call centre agent tells me, he can see I requested the downgrade in March but it wasn't successful. so Im liable to pay the outstanding amount. Whos fault is it that request wasn't successful. Im not working at the call centre. I did what I had to do, but the call centre didn't. They lady at the call centre told me in February that the downgrade has been done. Then 2 months later, Im liable for costs because she didn't do her job right. Really???