For more information and insight, read the article in AzureGuru.org
When you sign up for an Azure free account, you get a $200 credit that acts as a spending limit — that is, in the first 30 days, any usage of resources beyond the free products and quantities will be deducted from the $200 credit. When you’ve used up the $200 credit or 30 days have expired (whichever happens first), you’ll have to upgrade to a pay-as-you-go account. This automatically removes the spending limit so you can continue to get access to all the free products included in the free account. With the spending limit removed, you pay for what you use beyond the free amounts and this is charged to the card you provided.
If your subscription expires, you lose access to all the resources associated with the subscription. However, the Azure AD directory remains in Azure. You can associate and manage the directory using a different Azure subscription.
References:
Associate or add an Azure subscription to your Azure Active Directory tenant
