Praise be to Allah the Lord of the Worlds.
Contests in which participants are asked to send messages-via mobile phones-that cost more than usual and in which they are likely to win or lose (Win the prize or lose the cost of the sent messages) are forbidden gambling as states the Noble Quran and the Prophetic Sunnah. Also, scholars consider this one of the grave sins.
It is unlawful for companies to resort to such ways to make profit particularly since the party offering the prizes benefits from the high price of the messages. In addition, the fact that the prizes aren`t part of the corporation`s revenues doesn`t make the contest lawful. Also, their being presented by a party that makes profit out of the messages suffices for making it as such. Moreover, there is no other benefit for entering the contest save to enter the raffle, and we have already explained this in Resolution No.(150) by the Iftaa` Council.
The owner of the housing cooperation can offer incentive prizes to customers by asking them to send messages with regular cost without making any profit. And Allah the Almighty knows best.