Written notification about debt: Debt collection

I checked my credit score and it went down and saw I got sent to collections for $800.00. Googled the name and called the number I spoke to the agent asked her to give me information about why and what company sent me there and she could not give me a straight answer she said Charters Communications I told her I do not recognize that and began to ask her why they didnt give me a notice before sending me to collections they just sent me there without my knowledge of what this charge is, She began to tell me I had to pay it or wait 7 years for it to fall of she hung up in my face and they blocked me so that I wasnt able to call them back.