Originally Posted by Dr. HFH

Prior to departure (flying the first segment): Any changes to the first segment will trigger repricing of the entire ticket. If the price has gone up since you bought the ticket, the additional fare will be collected. If the price has gone down, there will be no refund. Changes to the cities will result in a charge of $125 plus repricing of the entire ticket. Again, if the price has gone up since you bought the ticket, the additional fare will be collected. If the price has gone down, there will be no refund.

After departure (flying the first segment): Changes permitted and are free as long as the cities and sequence remains the same. (I.e., changes to flights/dates/times are free.) Changes to the cities or the sequence of the cities results in a $125 fee. Changes to the number of continents will trigger repricing the entire ticket.

See One World Explorer Rules 16(a) 1 and 2.