Bad service from on air tv

I purchased a dstv decoder from on air tv, I have been trying to get hold of them ever since the decoder was delivered. Iv sent the emails, whatsapp massages, I even called but their calls go unanswered. It's funny how they can email me stating my debit order did not go thru, yet they can't reply to my massages. My decoder isn't working yet they want to debit my money