Delays to refund overcharged premiums

Liberty is due to do a refund for overcharges to me. I had to jump through all their hoops to get my own money back, by completing forms & supporting documents. Now that they have this all, they are yet again delaying the refund due to their own internal "payment backlog". The refund deadline of 5 working days, has been changed to 10 working days, as confirmed telephonically with Kiara at the call centre. Kiara was reluctant to assist with escalating the matter and states that Liberty is within their timeline for feedback and even though they know that they will exceed this, they refuse to assist with this proactively. Poor attitude in a situation where the client isn't wrong, is really not the correct approach.