PEP

I opened a pep account and single handedly Pep has ruined my credit score. I have asked them repeatedly and phoned in to say my pay date is the 15th of every month and that is when I will pay my account. They refuse to listen to reason and just say either latest by the 7th or you get rated with the bureau. I have contacted the Bureau and taking this further as they are marking me every month yet I pay every month, harassment calls up to 3 times a day 7 days a week 21 calls in one week after I have spoken to numerous consultants