Document What Your Builder Says in Writing
Home Builders frequently make promisses to do things when building your house. You must document those conversations. You can ask them to confirm their offer in writing but even if they agree to do so, they may wait and let it just pass away. Consequently, it is good practice to confirm every conversation between you and the builder by email so that you can document the promisses and offers the home builder made to you.
Write down a brief history of what happened that day and then email it to the builder. If their promise was empty, they will probably deny that it happened. This isn't what you want, but it will force their deception on that issue out sooner.