The Sri Lanka post office is taken to be a difficult, arduous environment, so people arrive replete with ire, irritation and low thresholds of understanding, and ladle that onto the situation, making the "perception" true in their experience.
While hamstrung by silly work flows, excessive bureaucracy, and constant supplies of "red tape," I recently found the post office to have some charming characters, a number of whom were keen to serve. Some had no idea how to, but you could evoke a smile, kindle some positive thinking, and if you showed respect and asked for help, it was forthcoming.
We often take the garbage with us that we complain about and we are literally "proud" of our distress. You could go, decide to have as good a time as possible, acknowledge the real service providers (even if you have to ferret them out), and help them to help you while feeling good about themselves for doing so, rather than showing them how well you can sputter and fruitlessly fume as you seek to demoralize any good intentions they may have.