Data banking means you can roll over and save any unused data. For example, if you’re on the 10 GB plan and you only use 3 GB for the month, next month you’ll have 10 GB plus the 7 GB left over from the previous month, for a total of 17 GB. So long as you pay your bill on time and do not downgrade your plan, your banked data up to 500 GB will never expire.