Refund withdrawal

I ordered from onecart like a week ago and in which one of the items where out of stock and I had to get my refund on my app wallet. Since the 31 August till today 7 September I have been trying to withdraw my funds but the there's always a transaction error. I called them the first day on Saturday and they said they will fix it but nothing. I've have contacted them again 2 times and they keep on telling me that they will fix it. It is not a lot of money but I am a student and every cent counts to me .