Hi Larissa,
What is the Ranking you have defined in FBZP. You have to define the proper ranking to achieve your requirement.
In case you want the particular House bank, acocunt ID to be considered in a particular case and do not want to Change the ranking order, then Give thi shouse bank , account ID in Payment Run by editing the proposal. In this way, the Payment run will consider this.
Regards
Amitash