Now, many sms with a gift become popular in Indonesia.
The mechanism like this. The company send SMS using 4 short code digit number to the customer to inform that he/she win a gift. Then that customer will go to the store (company) to take the gift with showing his/her hand phone that he/she receive sms from that company. Then the company will give the gift.
But customer can manually inject his/her hand phone inbox with fake message as through that message is come from company that give the price using Fake message Application
So, the company who wants run the mechanism like this should aware from this. There is no way to differentiate the fake or real message. Another way is to double check with data that owned by company and not only from customer hand phone inbox.