An Azure relational database service.
Hi Mark,
Did you ever upgrade your subscription to Pay-As-You-Go? Reason I ask is, under the terms of the Free trial if you don't upgrade to Pay-As-You-Go your subscription will be automatically disabled and eventually deleted, and there are no charges.
If you did upgrade to Pay-As-You-Go that allows more capabilities, and you still have access to the $200 credit during the first 30 days, however, it is possible to purchase services that are not covered by the credit.
If you navigate to your subscription in the Azure portal, on left menu click on Cost Management -- Cost analysis, then at the top click on View--CostByResource, set filter for relevant date range. In the results, what are the different resource types that make up majority of charges? You may click on arrow to the left of each item to see Service name and Meter.
If your credit card is charged by mistake you may need to create free billing support request. I can help you with that since the process can be confusing. In meantime please reply in comment below with details I requested above.
Thanks.
-TP