How to say no to PT?

I don't know if this is right sub to ask but

I (22M) am an introvert who doesn't enjoy being in public places. I recently joined a gym, thinking I could just go, do some exercises on my own, and leave (this sub really motivated me to take this step). However, the trainers at the gym keep pressuring me to sign up for personal training sessions.

There are three trainers, and each day one of them tries to persuade me to pay for personal training. Even after explaining that it’s not financially feasible for me, they continue to stand there for half an hour trying to convince me.

I'm not very vocal and don’t want to come across as rude. How can I get them to stop doing this? I thought about switching gyms, but what if I face the same situation elsewhere?