Payment removed from system? ??

I made a payment on 18 March and their invoice reflects this. Then I placed an order and it was 'hheld' because I apparently had an outstanding amount, this after the account was fully settled.<br> Called the call centre on Tuesday and was told that the payment was credited twice and then removed all together, they would sort it out and my order would be processed. THIS DID NOT HAPPEN. <br> Called again on Wednesday and it still has not been sorted out. I emailed my query as well and there is still no response. <br> Now they have in the meantime given me a different amount which is different to the one given last week. <br> Today is Monday and my order has still NOT been processed and there is a new amount they say I owe.<br> How do I owe something that I have paid almost a full month ago? ?