I read that he dubbed his own voice for the German release, so at least he got his own voice in one edition of the film.Gary Seven said:The actor who played Goldfinger was dubbed. His accent was too thick for the film.
Reading some more over at IMDB, i don't know how accurate this is but it says this.
A few scenes in the final cut of the film feature Gert Fröbe's real voice and not Michael Collins' dubbing.
The line, "Except crime!" at Auric Stud is one example, but more obvious is the dialogue spoken just after Bond escapes from his cell. Goldfinger's line, "The underworld will rock with applause for centuries" is Fröbe's original voice, as is the line, "It can be, I think the expression is, blown!"