Normally when u book via Eticket , u cant be upgraded to next higher class...for ex., u might have booked a 3AC , but u will be seen a SL instead due to repair or so...but if u want to upgrade to 2AC or 1AC even though if there is vacant in those classes , u cant in case of ETicket..In case of PRS Tickets u can be upgraded next to higher class for want of accommodation..the option left with those Eticket holders are they can get the LCC certificate from TTE and apply for refunds..that too via TDR filing through online only..PRS ticket holders can get the refund via at any reservation counters.....Jai Ho PRS..