you might check with a good paintless dent guy.
they have tabs that they glue on the dented area. then attach a slide hammer to the tab. then pull the dent out that way.
it works on thin sheet metal. but a bicycle frame is much thicker. i don't know if it will work.
body shops have a tool to weld studs in the dented area and pull the dents out with the studs. the frame must be steel to do this. again bicycle frames are thicker than sheet metal so i don't know how good it will work.
you could use a little heat to help the dent pull out. but i don't know how good it would work.