got a text message confirming reservation for a study room in "Southeast Regional Library"

same as other user:
"D!BS!  Your request for Study Room #1 in Orange Branch Library on 9/22/2015 9:00 AM is confirmed.
--
Sent using SMS-to-email. Reply to this email to text the sender back and save on SMS fees.
https://www.google.com/voice/"

don't want to contact back in case it's a scam

This is legit.  It's a service that our library--and apparently others--use for reserving study or conference rooms online.  When you confirm your reservation, you receive a confirmation text.  If it doesn't apply to you, then perhaps the real person reserving the room entered the wrong phone number.

I keep getting texts from them saying my room at Agave library has been confirmed. I have responded a number of times telling them to stop but it continues

this is from the local public library. My online book request has been filled. I can pick it up now.