Gia,
Unfortunately no, there is no possible way to replace the band on a FitBit Charge HR. I would have suggested contacting FitBit directly as soon as the problem occurred. I was very impressed with their customer service when they replaced mine free of charge a year out of warranty when mine died suddenly. Since your dad has tampered with the product, however, I don't believe FitBit will do much.
Here is the link to FitBit's contact page- http://help.fitbit.com/?cu=1
Hope this helps!