Frustrated client

Made a payment towards my loan on 11 April 2019 and called collections to tell them not to debit twice on the 25th of April but they went ahead and debited twice. Requested for the refund of that amount on 13 May and to date nothing has happened despite my calling everyday to find out what’s happening. Complaint with reference ********** was logged and was called by FNB loans who advised that I should allow 48 business hours for the refund to happen and that was on Friday 17 May. I’m out of options now with regards to this matter,