How can we pay a purchase order with a 'service line type'?

Summary:

We have a purchase order with a 'service line type' but we don´t know how can pay it, as the purchase order line doesn´t has an item we couldn´t recept them and for this reason we can not find the PO (available) to be able to compare it against the invoice

Content (please ensure you mask any confidential information):

Purchase Orders with Service Line Type to Confront to Accounts Payable

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