Accountant?? BookKeeper

Hello, I need some help. The company I'm working for right now is have a bit of issues with people not paying their internet bill. So a couple of years ago somehow stuff for messed up and so the majority of the internet customers that owe money really don't. But some still do. So I need guidance as what to do. Should we start fresh and wipe the bill clear since we took over picking up the mail and have copies of every check we have or should we do something else. thanks you guys