We used to live at Gables Edgewater (worst apts ever by the way) and we moved out in January. We left our...?

...forwarding address at the front desk for any charges they wanted us to pay. Today April 25th we received two letters of collection saying that we needed to pay our past due amount when we NEVER received a bill before. We don't even know WHAT we have been charged for! Is there a place that we can make a complain for this?? This is not fair. We have never received a letter of collection before and we don't want this to affect our credit just because their negligence. Any help pls??