First, this:
DISCLAIMER
This is from personal experience only. I am not an attorney nor do I work in the legal field. I speak only from personal experience in the legal system and sharing with you what I've been told. Be sure, before you act on anything I say, to educate yourself on the laws, rules, regulations, and so on where you live, before you run off willy nilly with a 'plan' that will suck in your situation
/End Disclaimer.
qft
This is in no way professional advice, however I dare you to find anyone in this community that has served more court-ordered community service in their life than me, over 1100 hours before my 21st birthday if you also count what the judge threw out.
Moving on;
Go to the courthouse and explain what happened. Let them have a police officer take you down the the place where you volunteered and explain your situation, they will listen.
NONONONONO NOOOO!
Not the judges out here, that will just get you in jail faster, giving excuses and asking for an officer's assistance to prove your case on very tight staff. You will have to go to court again soon for a followup hearing I take it? If you have time and if it's a very small amount of hours to serve, I'd just do them somewhere else that will report them (and it sounds like you do have few hours, but the court specificaly ordering where you should serve them might be the stiff here, you gotta oke around sooner than later on this one). It might be your best choice, especialy if you have nothing to show a judge the hours and days you put them in at the first place. IF you can produce some logs or documentation on your end showing the hours you put in and the efforts you've made since to get the hours properly reported to the court, then the judge might bother having a look at them but will likely dismiss them since they're documents you could of fabricated. I had the same situation happen to me and did what tupac jsut suggested, I went in there to explain I did what I was told to and said I would do anything to prove the discrepancy (including taking an officer or the judge down there or jsut giving them a call right there and then). The judge must of been in a bad mood because he wouldn't have none of it, chewed me out for "not doing anything more about it" from the time I supposedly finished the hours until the court date, and then "graciously" doubled the original sentence (double the community service), dismissed all of the properly recorded time I had previously put in, and gave me half the deadline I originaly had before on the lesser sentence to complete the hours. It was agree with him or go to jail. Take it from a person that had to crunch in 800 hours into less than 6 months (long story short: legalize it!), if you got the time left, just go out there, find a place that will properly report your hours and do them again, so then you can walk into court on your date and make the judge happy.
It sounds like community service is working as planned, as a deterrant against getting another ticket 
Community service works wonders in many ways, the real sad thing is people thing you need to do something wrong first in order to go out and invest some of your time in the community. Statistics have shown those that serve highway community service are not any less likely to be repeat offenders unless their offence was related to hazardous driving, most that serve highway community service do leave deterred from driving recklessly or in excessive speeds. They also showed that those that served less than two weeks (~80 hours) likely didn't learn anything to deter them from repeating offences or to drive safer, while those serving 150 hours or more on the side of a highway rarely afterwards drove faster than 10-15 miles faster than a posted speed limit or through a construction zone without being more cautious. In short the study recommended all licensed drivers serve a 150 hour stint in highway community service, because those drivers that have served for that time or more were the most unlikely to commit a serious traffic violation afterwards.
On the contrary.
You had the privelege of choice.
You chose to NOT slow your bellybutton down (or whatever the infraction was)...
Keep in mind before you go see the judge next time, you also hade the privelege of choice to serve community service rather than jail time, and they WILL remind you of this if you minutely tug on their string.
