More debits and less refund

I have a Wesbank cashpower loan since 2016, for the 1st time I missed 1 payment September 2019 and made efforts to make arrangement to pay the arrears over 2 months. End of October they debited full amount twice plus an arrangement amount, after numerous calls asking them to refund 1 instalment that they were not supposed to take.....I finally spoke to a collection team leader by the name of Alphonso and was moved from pillar to post. At the end I received less than half of my instalment. When I called Alphonso he just told me that my account was not supposed to be in arrears at the first place, apparently there's nothing he can do to assist. The arrangement that I made cost me money as other creditors couldn't get their money since Wesbank Cashpower debited 2 instalments plus half instalment. They don't treat their customers with respect, infact they don't value their customers.....can't wait to pay up this loan and I wish they can stop bothering me with new offers.