The Account record can contain many important pieces of information about how payments should be processed and handled for the given account.
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You can now store the payment method (Credit Card, Direct Debit, Payment in Advance, Invoice) in the account record. Depending on who the debtor is for you media campaign this information automatically transfers into your media campaign just like the Payment Interval, Start and Due Date.
Please notice that the field is using a Picklist Value Set 7.2.1.2 Edit Picklist Values Sets (Global Picklists) and the values need to be active for the respective record type. If not working contact your administrator.
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For invoices set to be dispatched via email, the the invoice email to be used is set on the Account record. Additional emails can be configured on the Media Campaign level.
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The Payment Interval, Payment Start and Payment Due to are all ways to configure when and how often invoices are created for a Media Campaign. These are configured directly on the Media Campaign. For more information, see here.
The beginning of the week is by default Monday (ISO 8601, but can be modified in your 7.2.1.1 Administration Settings or 7.2.6 Configured in your Legal Entities.)