Is 37 too old to be bullied at work?

I’m in a situation that I’ve never thought I would be in at my age. Vindictive, lying and just plain mean spirited people are saying the worst things about me at work. Now I don’t gossip, speak bad (or at all) on anyone, and I keep things professional. But that doesn’t stop them. They are like the mean girls High School clique as “Adults”. All I want to do is work and collect my check. But they are smart. They never say my name or confront me to my face so if I complain to HR the first thing they will say is “Did you hear me say YOUR name?” Or “How do you know I was talking about YOU.” I know it’s about me. I’m not crazy or stupid as these evil women think. I work in a call center in a small but important department so every conversation between calls can be heard. They deliberately so things they know only would effect me only and the whole team knows. I walk in the room at my desk and the snide comments made about me are said loud enough so that they KNOW I can hear them. They are trying to wear me down especially the one evil bitch who makes it her soul purpose to say the rudest thing around me. I keep quiet and just try to focus on my work but I don’t know how much more I can take. Physically they can’t really do anything to me. I’m 6 ft without heels and know how to handle myself somewhat but this is ridiculous that I have to go through this at my age. I’m pissed at myself for not seeing this coming and confused as to why. How do I deal with this? I swear it’s getting to the point where I think they have a bet to see who can crack me first. If I cuss them out I’m going to get fired. If I knockout someone’s teeth I’m going to get fired. I don’t know what to do.