I’m creating a new subscriptions with my current logged in user, but I’m getting error:

403 FORBIDDEN
{
    "error": {
        "code": "ExtensionError",
        "message": "Operation: Create; Exception: [Status Code: Forbidden; Reason: Tenant has reached it's maximum number of subscriptions]",
        "innerError": {
            "date": "{currentDate}",
            "request-id": "*****",
            "client-request-id": "*****"
        }
    }
}

after lots of googling and reading document, I still can not find a way to increase my maximum number of subscriptions. Anyone succeed at this problem can help me resolve it?