Delete Azure Tenant & "Work or School Account" that too closely resembles my Microsoft Personal Account.

Question

During some Microsoft Learning exercises, I have managed to create a "Work or School" account with the same email identity as my Personal Microsoft account; and with it an Azure AD Tenant.

I wish to retain my Personal Microsoft account (with my Learning progress and Ceritifications attached; not to mention Family associations etc.)

I want to completely delete the Work or School account (with the same email identity) and the AD Tenant (representing my personal "Domain") that goes with it.

The Tenent has No Subscriptions, No Resources, No Groups and a single user (Global Admin!?).

What I've tried:

1. From Azure AAD | Users | Edit user - I've tried changing the email address, keeping the domain but adding "-work" to the identity. This results in "(!) Failed to update user. Insufficient permissions to update some of the following properties: userPrincipalName".
2. From Azure AAD | Overview | Manage tenants: Select the only Tenant listed, click Delete. This results in a screen with the following "You do not have access":
   1. { "shellProps": { "sessionId": "78b131fe3abe422f963d474fb3790337", "extName": "Microsoft_AAD_IAM", "contentName": "TenantDelete.ReactView", "code": 403 }, "error": { "message": "You don't have access to this data.", "code": 403 }}