Whats out!! WebAfrica deduct money without authority

I cancelled my contract with them and returned their rooter. They even signed for it. Yet, one month later they billed me for it and deducted another R999.00 from my bank account, even though I sent them enough proof that the rooter was returned in good order to them. Their Whatsapp just closes after a while, they refuse to refund and they keep on asking for additional proof even though it was sent to them via their Whatsapp and e-mail address.