No, you can't change an enhancement. What you can do though is to delete the enhancement and then replace it with the enhancement you want, but it's going to cost you buying the replacement enhancement.
Hope that answered your question.
thank you 
i was just worried i had done something permanent that i couldn't change when i had no idea what i was doing.
how do i delete them btw?
Lets say you have the power brawl 6 slotted with the following enhancements.
damage, damage, damage, recharge, recharge, recharge
But you now want to throw in an endurance accuracy. You simply go onto your enhancement screen and drag the wanted enhancement over an existing enhancement you no longer want. So if you dont want one of the damage enhancements no more it'ld look like this;
damage, endurance reduction, damage, recharge, recharge, recharge
Thats if you place it over the second damage enhancement. Hope that helps!
@Damz Find me on the global channel Union Chat. One of the best "chat channels" ingame!
thank you both and sorry for being a noob
can i change the enhancements on a skill?
sorry if this has been answered elsewhere, i did look.