Nedbank staff horror and refusal of refund on an account over charged

i had a personal loan with nedbank which i called their legal dept to settle it on 11th Oct 2018. i settled same day and sent a proof of payment as per the amount that was given on my settlement letter. to my horror i was charged R29 790 on the 17th Oct 2018 and this reflected on my mobile banking application with Nedbank. i then queried this amount with nedbank and they advised that i was charged in error and funds will be allocated back to me. they advise i will be called soon for this to happen and sent an email confirming this on the 10th Dec 2018. till this day i have not received a call from them and have not received my refund. when i call their customer service line i am send from pillar to post and my they promise to call back but they didn't. this is a nightmare and a horrible service that i have to run around after a bank when they owe me and have admitted to their error on email, yet they cant pay me my money. i am beyond livid and disgusted at their service,.....to think i use to love and recommend them.