Microsoft Office - "Past due bill"

We keep on receiving emails from Microsoft stating “Your Microsoft Online Service bill is past due”

We took out 14 subscriptions for Microsoft Office 365 Business Premium from Microsoft in June 2018 where we had to make an upfront payment for June – March 2019 in order for us to start using the products.

In March 2019, we had to renew our annual subscription, we received a bill for the full year of 2019 and then we decided that we do not want to pay annually, but monthly instead.

They confirmed that it’s in order and disabled our annual subscription, thereafter we started to receive emails that we owe them for 2018 (9 months) and full year of 2019.

After a long telephonic discussion and various emails, they took off the 2019 bill due to us now paying monthly but still stated that we owe them for the 9 months of 2018.

We provided them with proof of payments, THEIR Admin portal also showed that we paid the bill for 2018 and that there is nothing due.

The short and the long is, we would have not been able to use the products if we did not pay upfront for the 9 months of 2018 AND we would have not been able to renew our subscription for 2019.

We have done everything from our side to resolve the issue.