Hello Doughnut,
I have the experience that it depends on the age of the lens. My slightly older Sigma APO 400 mm could not be re chipped, according to a list they held at the Sigma service center. Fortunately my 28-105 mm can have a surgery: it will take 4 weeks in Holland and will cost Euro 45 ex tax for everyone..
Good luck with yours !
Aerovet