Payment not matched to online order

On 27th November I ordered 2 x filter cartridges for our office water cooler online. Payment was made on 28th November. When I heard nothing further a couple days later I went to track order and it said payment deadline missed. I have since emailed my proof of payment twice and followed up with emails and phone calls only to be told repeatedly that accounts have not yet matched payment to order!! It's impossible for a payment made on 29th NOT to reflect on your bank account, so what is the hold up? I did not miss payment deadline in the first place either.