My question involves landlord-tenant law in the State of: New Jersey

So, I recently moved out of my apartment to work at a summer internship overseas. I've settled all my rent, got my security deposit back - but now, 3 months later, my parents receive a bill (I'm having my mail forwarded to their place while I'm out of the country) for garbage collection/water for the last four months of my lease. (Note: every month, I get an invoice for rent + garbage collection/water, which I pay together in one check. It was specified not in the lease, but in the "welcome" package they sent me.)

Unfortunately, in the rush to move/pack, my parents can no longer find the original rent invoices. I have images of all the checks I've sent and the amount I paid from my bank, and we should still have the lease that specified the amount of rent I pay every month. A simple subtraction should show that I paid these bills.

The main problem is that I am out of the country, and my parents live out of the state, so we can't resolve this in person - and the ex-landlord is being very persistent about this matter. I'm particularly worried about my credit rating being affected if he chooses to call a debt collector (hell, from the letter my parents received, I don't even know if he's already done so!).

What legal recourses do we have to protect ourselves? Is there any tenants' rights place that takes phone calls/e-mail complaints? I'm hoping if there's a place like the BBB for landlords, maybe a phone call or complaint or the threat of such will make him back down. If he sues me, there's no way I want to waste the $1000+ airfare to fly back to the US just to deal with him.

Is there any way to possibly appoint my parents as proxies in my place? And is there a way to seek legal advice (if it becomes necessary) outside of NJ? My parents both have jobs and can't just up and drive out of state to settle this.

Any advice or help would be greatly appreciated!