How can I extend the Rate Plan Expiration Date

I currently have the following account summary

My question is: will I not able to make phone calls on Dec 23 2013 since that is the expiration date for my rate plan. I have just added 60 dollars into my account, but the Rate Plan Expiration Date has not been extended. I am worried about I will not able to call or text after that date. Could anyone tell me what I should do to extend the rate plan expiration date?

Thank you very much!