Like Dennis said, it's free but you will see partial charges. Your rate plan is a monthly recurring charge so if you make a change before the end of your bill cycle, you'll see partial charges. You'll probably see a credit based on days remaining on old plan before you changed the rate plan, and charge for the remaining days in your bill cycle for your new plan. To avoid this, make the change in SelfServe on your invoice date. Go to SS and look at your bill - what's the date on it? For example, mine is the 24th so if I make a change on the 24th of any month, I'll avoid this!!