Unprofessional Work Etiquette

I'm currently a Justine consultant. I've recently received constant reminder about an overdue balance which does not make sense to me. I have made a payment last month on the 14 August the payment did not reflect, I sent multiple emails with my proof of payment. This is unacceptable as I've seen another consultant with the exact same complaint.

I called the Justine call center earlier today and the lady I spoke to said I should send an email with proof of payment, I explained her that's i have sent an email to credit control. She told me that they are up to date with their books and it should reflect along with that she can't do anything about it as it's the credit control department. So I asked if I could contact them if it was possible to call the credit control department and she responded saying they only respond to emails.

This is pathetic service and purely unprofessional.