'Haywire' Star Gina Carano -- Vocally Challenged In Flick

Gina Carano is the REAL DEAL in the world of MMA ... but there are allegations she's not totally the real deal on the big screen ... because her voice in the new movie, "Haywire" ... may NOT be her voice at all.

Sources connected with the production tell TMZ ... the folks behind the movie didn't like the way Carano sounded when they filmed the flick ... so they changed it in post. It's unclear if they used fancy electronics to alter Gina's vocal quality, or whether they dubbed in another female voice.

Monday night, Carano was at The Grove in L.A. ... where she totally spoke with us ... and sounded great ... at least that's our opinion.

We placed multiple calls to the production company ... so far, no comment.