I was hared by text today... What do I do?

I can't find out WHO the texter was, but I did a reverse lookup and found out that they are on t-mobile. I called T-mobile's hotline, but none of the options matched even VERY vaguely what i wanted. I actually want to just find out who it is, because that way I know which of my friends gave out my phone number. What does anyone suggest I do?