What to do about pass bill?

I recently moved back to Colorado after living out of state for nearly 5 years. When I lived here last time my husband and I had rented an apartment where the complex transferred utilities to our name. We never received a bill from the utility company. We went so far as having our mail held at the post office and we would pick it up since we never received our mail box key. My husband was set to deploy and had already left for training when I moved back to California, since we had a new born son and my husband wasn't going to be home we where able to break the lease. I also called the utility company and was informed they where never put into my name. Now that we have moved back I set utilities up in my name and was told I would have to pay my back due balance the only issue - they already sent the account to a collection agency. Since me paying them off isn't going to remove the collection account what should I do? I have no issue paying the utility company or the collection agency, but im not going to pay two companies that same amount of money. I have already contacted DOMA with the issue asking for help from them on what needs to be done.