Sometimes they use an 800 service. Also watch for ER Solutions 877-495-0497. who collects for Verizon. Also Convergent Outsourcing who is part os LVNC LLC - they go by other names such as Sherman Financial. These are also Verizon anong others onversion Outsourcing is 859-586-9558.
If you are being harrassed - remember to check the statute of Limitations on the type of debt and State and remember - they debt they are calling about is always an "alleged debt" to you. If ytou own up to the debt- they can go after you even if the limitation is through.