Payment of an account that has been written off - company filed bankruptcy

What is the name of your state?
i live in texas. the telephone lines of the apartment complex in which i live were owned by a company called coserv. this company has several divisions, i.e. gas, electric, phone service. only the telephone line division has filed bankruptcy and are now operating as advantex telecommunications. they will not provide me with phone service nor release my phone lines to another company to provide service until i pay what they say is a past due account from previous service with them. if they've written this off, turned it over to a collection agency, filed bankruptcy and are operating under another name, am i still expected to pay this debt? aren't uncollected debts part of a bankruptcy?