The following is the best solution that I know so far...

Setup a wifi internet connection at your home in nepal, get a Nokia phone or an iphone for your parents and install skype app in it. Teach them the  few extra clicks needed to make calls from skype. If you add $10 to their skype account they will be able to call any US/Canada numbers for few cents per minutes and trust me that $10 can last upto a year.