Window modernization, KFW funding; difficulties with energy consultant

Hello,
a question for the experts here. We have a certified energy consultant who applied for the KfW funds (430;431) for us. Who can you contact if you do not agree with the support during the modernization and especially the submission of the invoice amounts to the KfW for reimbursement? Who is responsible?
Specifically: We had new windows, sun protection/external roller shutters, and a new front door installed for our single-family home. In this context, the energy consultant applied for KFW 430 and 431. In practice, there was no construction supervision. Documentation (photos of before/after) was not done on his part. He was on site once in connection with another energy consultation (one year before the planned window modernization) and then when the windows were fully installed. In this context, various painting works inside and outside were necessary, especially because of the new external roller shutters and the electrical installation for the shutters. Now the energy consultant is reluctant to include the painting invoices in the claim. At the same time, he demands double the flat fee that was previously (unfortunately verbally) agreed upon. Who can I contact to clarify this case? Meanwhile, there are negative entries about this energy consultant on the internet. Many thanks for constructive tips.

Go to the Verbraucherzentrale. Unfortunately, almost anyone can call themselves an energy consultant.

Now the energy consultant is having difficulty including the painter invoices in the claim.

If they belong to the measure, they must also be submitted. The reference to the measure must of course be clearly identifiable so that the caseworker does not object. As far as in the automated procedure the consultant is the submitter, I would instruct him accordingly and, if necessary, hold him liable.

Unfortunately, almost anyone can call themselves an energy consultant.

... which, however, must not mean equating incompetence with a certificate of competence ;-)