Disappointed long term client

There was double payment October. One manual and the other debit. I was told instead of a refund it would be utilised for November, however in November there was another debit order. When I called they told me they now can’t trace what happened to the money. They would lodge a query and get back to me in 5-7 days. Still I haven’t received any feedback and another debit order went through for December. Who claimed the money if now it can’t be traced but it appears on the system?