In Russia, Kazakhstan and Belarus
Russia
Only companies listed in the FSSP register (ФССП, the Federal Bailiff Service) may work with individuals' debts (Law No. 230-FZ). They may call no more than once a day, twice a week and 8 times a month; they may not call at night (from 22:00 to 8:00 on weekdays and from 20:00 to 9:00 on weekends) or make threats. After 4 months of delay, you can use a notary or a court to refuse contact with collectors or to allow contact only through a representative.
Kazakhstan
In Kazakhstan, collection agencies operate under the Law «On Collection Activities» and must be listed in the register of the Agency for Regulation and Development of the Financial Market.
Sources: Federal Bailiff Service of Russia («ФССП России»), Federal Law No. 230-FZ on the recovery of overdue debts («О защите прав и законных интересов физических лиц при осуществлении деятельности по возврату просроченной задолженности»), ConsultantPlus