Update two models that have belongs_to relationship

I have model Program and model PointOfContact. Program belongs to
PointOfContact. There is a form to update values, which shows attributes
from both models on one form. What is the best way to update the models
with one call. I tried this and it did not work

Controller code:

@program_old = Program.find(params[:id])
@program = Program.new(params[:program])
@program.id = @program_old.id
@point_of_contact = PointOfContact.new(params[:point_of_contact])
@point_of_contact_old = 

@point_of_contact.id = @point_of_contact_old.id

current_user = session[:user].login
@program.updated_by = current_user
@point_of_contact.updated_by = current_user
@program.pointOfContact = @point_of_contact


This does not work and gives the error:
Violation of PRIMARY KEY constraint ‘PK__point_of_contact__1F2E9E6D’.
Cannot insert duplicate key in object ‘point_of_contacts’ …

Doing update_attributes on individual model works but that is two calls?

Is there a better way to do it?