What normally happens is the customer complains directly to the bank. It could be to a staff member. It could be to a manager. We call that the first level of the complaint. I think the goal is for the bank to resolve those complaints with a customer at that first instance.
If a complaint is not resolved, it could be bumped up to some level within the organization, and a second set of eyes within the bank would look at it. Normally about 90% of complaints are resolved within the bank. There are some complaints for which the customer is not happy with the outcome recommended by the bank. In such cases, it is the customer who decides whether they want to take that to the external complaint body or accept the bank's recommendation.