Notify your bankruptcy attorney right away. They can take action with the Bankruptcy Court to get it stopped.
If Green Tree, or any of your creditors are violating bankruptcy court orders by calling you and trying to collect from you after you have filed bankruptcy, and they don't have permission from the Bankruptcy Court to do so, the court can punish them.
In a recent case, a bankruptcy court in the Northern District of Texas found that Green Tree had violated the chapter 7 discharge injunction, and also the chapter 13 automatic stay, by calling the debtor and trying to collect after she had first filed chapter 7 and been discharged, and then years later filed a chapter 13 (for other reasons). In re Loe, Bankr. ND Texas 2013.
The court awarded the debtor $1000 in actual damages, and ordered Green Tree to pay her attorney fees of $20,212.70. The court also found that Green Tree "willfully and intentionally violated orders of this court" and assessed punitive damages against them of $25,000 "which the court considers sufficient to deter similar conduct in the future."