Cell c No Reimbur*****t has been done in almost 3 months

At the end of October I accidentally paid cell c twice. I asked for a payment to be reimbursed into my bank account and they claimed its going to be done. I have been calling them ever since and they been claiming the payment will be done before the 25th December. I explained that I have other people to pay and require the payment. This is unacceptable.