Take the UFC for example. They pay people $300 to do piracy investigations bars illegally showing the fight by not paying commercial rates.
When they catch you, a lawyer sends the bar or restaurant owner a letter threatening legal action and a hundred thousand dollar fine, unless they agree to settle with them for $10,000.
The attorneys are just fishing when they send out the letters. People get the letter and the first mistake they do is call the attorney.
All you did was acknowledge you received their letter, and provided information to the attorney how to contact you and pressure you into paying.
You throw away the letter, they don't know if you got it or not, and the only way they can tell if you got it, or of they even got the right person is to hire a local attorney, file a lawsuit and pay to have you served.
Chances are they are only going to go after the ones who respond to the threatening letter.
I know this because I used to do piracy investigations for the UFC.