oneworld - Oneworld tickets - "service" fees

Most (all?) of the oneworld tickets allow free date/time/carrier changes provided the ticket routing is unchanged. However, I've seen some reports of airlines charging "service" fees to make those free changes. How common is this?

The last time I needed to make any changes to one of my RTW or circle trip tickets was in 2009 (a date change with BA at FCO. They changed the date without a problem, though forced me onto the BA code for the connecting QF flight).

Seeing it more and more, especially from a certain marsupial.

Seeing it more and more, especially from a certain marsupial.That's been happening for years.

I note my last AA ticket LONE4's required a service fee to ticket (NZD60 per PAX ex AKL) but at least contacting them for changes saw no additional fee imposed.

And many AA GSAs charge issuing service fees (South Africa,Pakistan)

And many AA GSAs charge issuing service fees (South Africa,Pakistan)... yep as posted, AA's GSA in BNE (via NAN), charged those issuing fees, but no fees when changing flights.