How can I understand who is the owner of a phone number???

[darklight_]

I received sms from an unknown number and I want to understand who is the owner because Im almost sure it is someone who knows me. Im from bulgaria. I tried some online sites but most of them just gave me a nickname of the person...can you please tell me about a better site or another way of finding the id of that person...thank you!!!

 

[rgd1101]

Sms back to ask who it is.