not just complaining in general but submitting "official" complaints to companies, any of you ever done this?

my mum has a friend who does it on an almost weekly basis, most of which i assume are completely fabricated, she writes to all the major food companies to state her dissatisfaction and quite often gets free samples/vouchers for her troubles.

i complained about a rail employee via email last year after we had a series of bizarre stand-offs during which he told me to fuck off, got a letter of apology, some bullshit about him being spoken to by his manager and £25 of rail vouchers i've never used