If you're seeing unexpected charges after canceling your Azure subscription, it's possible that the charges are for services used before the cancellation took effect. Azure bills in arrears, meaning that you pay for usage from the previous billing cycle.
However, if you're confident the charges are incorrect, you should indeed get in touch with Azure Billing support.
You can create your ticket by using
but if have deleted your subs. and still got the error
you can try twitter to contact with support team