53, you are welcome to change your plan at any time...but keep in mind that whenever you do that, your OLD plan airtime allowance AND minutes of use are prorated for however many days you used them in your current billing cycle...

And...

when you change your plan to a NEW plan, in addition to it being prorated for the amount of minutes and airtime for the rest of the time you are on the current billing cycle, you will also be charged for a month in advance for the new plan.

Figured you might wanna know that since your bill when you get it next month will be all sorts of funky. 😃