PSE&G Public Service Enterprise Group Overbilling nightmare Internet

My gas bill for December 2009 is THREE TIMES the normal amount at a house that is empty.  I am selling the house in Burlington.  I moved out on November 2, 2009 and left the thermostat set at 60 degrees. I go down a couple of times a month to check on the house.  NO ONE is living there so I cannot understand how it is possible for my gas bill to suddenly jump to three times the normal amount.  I explained this to the representative who said "Well, the weather has been in the 'teens."  That makes no sense.  The thermostat has not been touched in TWO MONTHS.  I asked to have the meter checked for accuracy as well as the instrument used to read the meter and was told no.  I believe that this bill is absolutely inaccurate.  How could gas usage suddenly jump to three times the normal usage when the thermostat has been set at 60 degrees since November 2, 2009 in an EMPTY house?  Why wouldnt the prior bill show the same amount since I havent lived there in TWO consecutive months?