I use mine all the time while charging, the battery always seems to need charging, so I have to do this very often! I have never heard that it is not ok
My phone stops charging when it's in use even if it's still attached to the charger. I don't think it hurts them to interrupt it while it's charging. I do it all the time.
It is OK to use my phone while charging; I remember that from reading the manual (and I've done it a bunch of times). I don't know if that is true for all cell phones, though.