goddammit credit agencies!!?

When I turned 18 I got a phone line activated and I disconnected a few months later due to horrible service and never paid my bill of 30.00. Well that was almost 2 years ago when this happened. I have moved from my place and never have recieved any returned mail from the phone company. Well I guess the account went delinquent and now they are charging me over 200.00!! The credit agency finally found me September 7 and contacted me the first time to tell me about this, I haven't recieved a single piece of mail or a bill from these guys, so this is the first time hearing about this. Anyways, They said that they wanted this paid off right away and I said hey hold on I need a bill or something from you, you guys could just be any joe shmoe calling me asking for money. And they told me that they would send me something in the mail. Well it's been a month and I have yet to recieve anything and they keep calling daily and I keep telling them that I need a bill. What should I do?