How to Avoid Text Scam

Last Sunday, my sister was scammed thru text. I have a brother living abroad and my sister received an unregistered number and thought that it was my brother. The text goes "kumusta kayo dyan, malamig dito" and she replied to the text and the next text she received goes like this " ang mahal ng load dito, gusto mo magbusiness, yung 500 na load dyan doble dito". My sister believing it was really my brother went to buy 5,000 worth of Globe prepaid card and sent the pin to the number. She never verified with my brother if that was really him. They even bought the sim cards from a seller and even cautioned them that there are a lot of scam similar to that. They never doubted the person texting her ( she was with my mother).
So when I met them that Sunday and I learned about that, I immediately checked the pin code if it was used, we were lucky to load 2,000 worth of load to our cellphones, the 3,000 load was already used. It seemed that the scammer was also loading the pre-paid cards during that time. It was a race against time reloading the prepaid cards.

Lesson learned. Do not trust unknown text especially this season of Christmas.