While travelling one of the options is to request some young man who has a lower berth to exchange his berth with the upper berth. Another option is to cancel the ticket and try afresh to get a lower berth in which case there is no guarantee that while booking next time a lower berth will be available as there is a good chance that all the lower berths are exhausted. One can also try to get a lower berth by booking one's ticket by logging into IRCTC website and at the time of booking exercising the option "Book my ticket only if at least one lower berth is allotted."