Dstv don't care

My husband has been waiting for he's refund from dstv since end of July. He mistakley made a payment bigger than the installment and has been trying to resolve this issue with dstv almost every week not even a manager is able to get this issue resolved. We pay our dstv installments every minth without fail even though we still struggling with this issue. The last my husband was told is that they're waiting for finance department we've sent through proof of payment showing we paid that amount and also we still paid the installment amount so that they wouldn't take money off the amount we need a refund on. This is terrible we've been with dstv for years and this isn't fair.