You could create a workflow that simply has the Clear Approvals task and assign the document to that workflow and then back to Payment Details, where it should pick up the payment status. From my assumption, this would again send the workflow to the complete status as it currently is.
Alternatively, a potential workaround could be to use the Content Type > Advanced tab and set up a single task for Clear Approvals. Once this is in place, there will be a Run Content Type button at the bottom of the Content Fields section while viewing the document. Be aware that this would apply to the entire content type, so I would suggest that you add this in, run it for the one where you want to clear the approvals and then disable it. To the best of my knowledge there isn’t a way to delete these actions in the Content Type > Advanced tab once they’ve been created.
I would suggest that if a workflow is complete, this means that the document was either approved or no approvals were required in the workflow process. If complete the document will not have pending approvals, check your workflow and see if there is a variable called Is Approved on the approval step to move to the create and validate. Pending approvals is a variable but in the document above this document shows the approval buttons due to the interface not because it’s not approved.
Check Is Approved and Pending Approval variables to validate.