Refunds and broken items

I bought two Russells hobbs 6L pressure cooker. Upon delivery both boxes were unwrapped and unsealed. One pressure was broken. I logged a return immeadately . The came after 2 days to pick up my things . I asked for a refund instead of a replacement. I was refunded half the amount. I have been trying to get them pay the remaining amount but to no avail. I have been send enquiries and emails but still my issue has not been resolved