No refund on 360 box

I took out a new contract with Virgin Media in November after leaving sky and wanted a 360 box instead of a streaming box. The local agent who signed me up said it would cost me an extra £49.95 one off fee but he would get it refunded on my bill. This has not happened even though I’ve spoke and texted him a few times regarding this. He’s says it’s been sent off to Virgin Media but nothing is showing on my account. How do I escalate this with Virgin as it was all dealt with via this agent?