hotspot voucher reloads ticket time if login page refreshes

i am having serious problem with my voucher ticket, if there is connection time out or login page refreshes or maybe the switch/router/wireless devices goes off, their ticket(my clients) that has almost finish will start counting afresh from the beginning and has been happening for some time now, and i am loosing seriously in business, i dont know what to do and how to correct this bug.
please someone should help me out.