Cancel an invoice by ID, with the option to force cancelation when no contact information is present.
Cancellation will require either an SMS or E-mail to have already been set if the invoice has proceeded to the point where it may have been paid.
|invoiceId||The ID of the invoice to delete.|
When omitted, this will be false.
$cancelInvoice = $bitpay->cancelInvoice("QrPWSMkq594kQfJex28S7X");