Stop contacting them at once. Don't send anymore statements and don't call them about their debts. The bankruptcy court issues an "automatic stay", which halts any attempts to collect a debt, once the debtor files.
If you have secured debt, you can contact the debtor to see if they want to "re affirm" their debt. This means that the debtor indicates that despite the bankruptcy filing, it wants to keep the property. In exchange, the debtor has to continue to pay the debt. If the debtor doesn't want to pay the debt, the debtor can abandon the property. If the property is abandoned, the secured creditor can go retrieve the property but cannot seek any additional funds from the debtor.