After you have hired an attorney but have not filed bankruptcy, you can tell most creditors that you have retained an attorney for bankruptcy give them your attorneys name and number and politely ask them to contact your legal representation. If they have an attitude, do not get upset, but ask them for their full name and supervisor's name and number so that your attorney may contact them. That usually ends it there.
I always recommend writing down the name, date, and time of call as well as the content of an unpleasant or sometimes downright nasty phone call. One thing you will probably have creditors ask you for is your case number. That is the number the bankruptcy court gives you when you have actually filed bankruptcy. You can usually tell when you are dealing with a collection agent who has no clue what he is talking about when he keeps asking you for your case number after you tell him you have not filed, yet.
When your bankruptcy case is filed, all listed creditors will receive a notice from the bankruptcy court stating you have filed bankruptcy. Upon filing, all legal and collection proceeding must cease by law. If you get any calls, ask them to contact bankruptcy attorney. If you get any letters forward them to your attorney. It usually takes a few weeks for the word of your filing to be filtered through most large banks, collection systems or given to any collection agents.