Are you keeping track of your Azure consumption? Under MPSA
(https://www.microsoft.com/en-sg/Licensing/MPSA/) your azure consumption will not be shown in your typical subscriptions screen, it will instead be mailed to your subscription admins once every 2 weeks. I plotted out the usage in a graph to see the usage. From there I can plug in the public costing rates (https://azure.microsoft.com/en-us/pricing/calculator/) to estimate how much it is costing me. (Although MPSA rates should be a bit lower)
This is necessary because agreements like MPSA and its older counterpart, EA (Enterprise Agreement), do not run on credits that you purchase in advance. While it keeps the service from suddenly expiring due to credits consumed totally, it does mean that you can overrun your expected usage without your knowledge. Even more, billing cycles for MPSA run every quarterly, whereas for EA it runs annually. Don't wait for the bill to come in before noticing something is amiss.
Keep track of your costs people!