Paying VPC and dont reflect. and late invoices

I have been paying my VPC account every time but it doesn't reflect, and i have seen that the same invoice that were paid is then reissued with a new date with the status of not being paid. Then also, if an invoice is issued you have a 60% discount when paid within a month, but the invoices on their system appears like 3-4 months late so i don't qualify for the discount anymore, because of their system fault, i will only pay the discounted amount and wont pay the full amount because its their fault. I hope to receive a response ASAP!!