Paying SSDA and they still trheatening

Owed Cellc R168 and they charged me R299. Reverse debit order after i could not get answer why. Month after SSDA contacted me claiming R305, R434 and last balance R503 within a week. Made arrangements to pay off as consumers does not have any rights these days. According to Cellc and SSDA, i was suppose to pay and then put in complain. Already payed R200 and recieved confirmation. Now they send threats via sms for me to pay R438.. Responded with whatsapp and email but no answer. Like CELLC