Multichoice ignore requests to process credit for decoder charge

Enquiry Reference Number: ***1

Multichoice charges me R89 more monthly for a new decoder I never received. My contract to upgrade to a DSTV Premium package (Black Friday Special) was cancelled on 22 December 2021, but Multichoice still charged me R89 in December 2021 and January 2022 for a new Explora decoder. Since December 2021 I've sent numerous requests to Multichoice to credit me for R178 (R89 x 2 months), but they just ignore my e-mails. I get an e-mail every time I send a request that they will urgently investigate the matter, but nothing happens. I honestly don't know what to do anymore. My last resort will be to instruct my bank (FNB) to reverse the debit order, but that will cost me a R40 transaction fee.