Harassed by Ackermans

For the last few weeks or so I have been harassed by Ackermans call centre agents, receiving at least ten phone calls a day for an account that is actually up to date. I had paid my instalment on the 17th of January, instead of the usual 25th of each month. The amount of harassment that I have received for paying an account earlier than usual is incredible. The have now listed my account as missed payments in January and February, and this has gone onto my credit record. Despite my informing their accounts departments over numerous emails that I have never missed a payment, I may have paid less than the required instalments, but have never actually missed a payment. Despite this, I continue to be harassed with increasing phone call on the hour every hour until 19:00 at night. This has been incredibly frustrating. I cannot wait to pay this account in full and never support this business again.