got hey (facebook name) and then no reponse

Got the same text as above folks BUT.. I called the number from my GMAIL account and it is a place where you can get and receive "your own free texting number".
Do not text them back.

Got a text from this number saying hi Mica, and i did not reply because i already had this happen yesterday from a different number, googled the number and saw it is spam apparently. just deleted the message.

Got a text from this number saying "hi Andrea". I texted back "who is this"?  Got a text back saying "Sorry !! Mi Iphone 's gonna die :(.

No messages after that.

Got a text from 774-642-6139 saying "hello Lee???".  I decided to google the number and see if anything comes up.  I don't know anyone in this area code and it appears that they have done this several times.
Any suggestions on how to block this number?