I know that costs that increase with sales volume classify as variable costs and costs that remain fixed irrespective of sales volume classify as fixed costs. (Correct me if I'm wrong or less appropriate)
By this understanding, say if the sales volume increase, the complaints increase, and hence we will have to hire more customer care/service executives with increasing sales volume. This logic makes customer service costs variable.
However, I have seen some people arguing that customer service is a fixed cost. I want to know the rationale behind their thought. It really fudges my whole understanding of the concept.
In search for some insights and deeper understanding.