Full description of the MC procedure on processing complaints and appeals is available here
You can send your complaints or appeals on the following contacts:
by email - This email address is being protected from spambots. You need JavaScript enabled to view it.
by regular mail - 121609, Russia, Moscow, Osennyaya str. 17, block 1, suite 1, room 146
personally to the Moscow office - Vasilisy Kozhinoy str. 1, office 17