The contractor wants to issue an invoice for planning services

I can understand both sides. The BU sees it this way: the OP requested a draft plus changes and adjustments to the construction description and wants to be paid for it (planning services at the customer's request). Certainly, he should have pointed out the costs, but the OP could also have independently informed himself about possible costs when making changes to the initial draft.

If someone commissions something without asking about the costs, one should not be surprised by the invoice.

If someone commissions something without asking about the costs, they shouldn't be surprised about the invoice.

Nothing was commissioned. The general contractor was asked during the offer phase to revise his offer. You can calmly lean back as a customer and let the general contractor work - unless he reports that it will cost something. No matter if it's a general contractor or a car salesman. Just because I want to change the configuration doesn't mean I have to pay for the replanning of the car. This is simply ridiculous, how wildly people are discussing here. The legal situation is clear. The general contractor is the "loser" - he must communicate beforehand that his offer will cost money.

When he makes drawings, that is something different: "After our conversation, he created a draft which we had adjusted again because it turned out too large."

"After our conversation, he created a draft, which we had adjusted again, as it turned out to be too large."

Exactly there, in my opinion, it depends on whether it was communicated as "without changes we won’t come together" or as "after the change we are in business." I am not a judge – if I were, it would come down to a settlement or mediation.

We have had this kind of threads regarding architectural services enough times. And I can't remember the result being "we don't have to pay anything"; it almost always ended up with a reduced amount below the HOAI. Just by the way, I also didn't commission the planning services of my architect directly. He came to visit, took everything down, and brought a first hand-drawn draft on the second visit. At the third visit, including the design planning, he asked if we wanted to continue; if not, he would have liked to have the invested time compensated.

And where is the difference now? I see no big difference, except that the fee regulations offer architects a bit more guardrails and thus partially protect them.