I couldn't think of a better word than reclassifying, but my question is best illustrated with an example.
Assume an elven first level fighter takes Weapon Focus as his 1st level feat and Weapon Finesse as his fighter bonus feat:
Could he, on going up a level, take Toughness as his new feat by re-classifying Weapon Focus as his second fighter bonus feat?
Or would this be retraining?
At 1st level, and at every even level thereafter, a fighter gains a bonus feat in addition to those gained from normal advancement (meaning that the fighter gains a feat at every level). These bonus feats must be selected from those listed as Combat Feats, sometimes also called “fighter bonus feats.”
Upon reaching 4th level, and every four levels thereafter (8th, 12th, and so on), a fighter can choose to learn a new bonus feat in place of a bonus feat he has already learned. In effect, the fighter loses the bonus feat in exchange for the new one. The old feat cannot be one that was used as a prerequisite for another feat, prestige class, or other ability. A fighter can only change one feat at any given level and must choose whether or not to swap the feat at the time he gains a new bonus feat for the level.
I assume this is the ability you're trying to use? If so no. It's only every 4 levels and it has to be a Bonus Feat from the Fighter class, not just any combat feats you have.
Retraining is what you would have to use.