There are 2 ways:
1) to Set up VoIP at home and take out the operator multi-room. It may be difficult if limited in time and had not previously encountered. Hand on heart, nothing beyond do not have to do.
2) Take ulagu like this: www.corp.mts.ru/fix_connections/intellect_services/logicline_of/
(not PR, just this hearing, I am sure that many operators will gladly offer the same thing). This option may be more expensive in terms of monthly payments (have to look), but no equipment and/or software does not need to buy/configure/maintain — asked the logic and the platform operator switches calls: voice menu, vremennye conditions, etc., etc., the Calls will come to Your sushestvuet city number (a link), or having access to the Network IP phones (may be cheaper in terms of cost calls, many operators offer)