Im pasting information about rollover minutes of your AT&T plan, directly from their website
Question: Do I lose my Rollover Minutes? How are rollover minutes expired or forfeited?
Answer: Minutes will expire from your current Rollover balance when the minutes reach an age of 12 billing periods. This normally means that if you have minutes in your current Rollover balance for about a year, they will expire. This does not mean you will lose your entire current Rollover balance, but just those minutes that have remained for 12 billing periods. Minutes that are not 12 billing periods old will stay in the current Rollover balance until they are used, or they expire when they reach an age of 12 billing periods.
The following conditions would cause you to forfeit your Rollover minutes:
Changing from a Rollover plan to a Non-Rollover plan.
Changing from a Rollover plan to a Military Plan.
Changing from a FamilyTalk Rollover to an Individual Rollover plan unless they are the last member to leave the account.
***Changing to a new Rollover plan where your existing Rollover balance exceeds the Anytime minutes of the new plan. Only minutes in excess of the Anytime minutes in the new plan are forfeited. This will take effect at the end of the billing cycle. (NOTE: AT&T Unity plans are an exception to this rule and you will not lose your accumulated Rollover minutes when changing to a Unity plan.)
Moving to/from Reseller to AT&T wireless service.
You can view your Rollover balance and the upcoming expiration date of Rollover minutes on myWireless Account in the My Current Usage section.
The paragraph with *** pertains directly to your account. Im surprised no one at AT&T told you this when you switched. I have a few relatives with well over 3000, and 10,000 minutes, and none of them will switch till they use all the minutes.
My own personal suggestion and belief is this.. "If you are on a plan with too many minutes rolling over, (as you are) then its time to lower your plan, forfeit what you didnt already use as its still costing you money to keep those, and start fresh"