Can I get a new SIM card for free?

Hi, everyone! I am new and stuff. I got a new SIM- card 4 months ago and now it got messed up somehow. I just put it on after a day and then it started asking me for a PUK code. I didn't know it and I tried to enter whatever it was for a long time, but then it just started rejecting my SIM. I went to the net and asked what should I do and they said I should get a new one and they said it was going to be free. Is this true, that is where I need your help. Can you help me, please? Ps. It's AT&T.