I think you misunderstand. There is no law against collection agents calling debtors.
The collection agency can not have a robot call.
I wonder now about my doctor, my dentist, my hospital and etc that have a robot call a day in advance to remind me of my appointment and sometimes leave a voice mail.
If you want to have fun with them, provide your doctor with the phone number of your dentist, and vice-versa.
Back in the 70’s there was a Unitarian church here who had a “dial-a-prayer” line. I gave that out to folks I didn't want to hear from. I also used it as my call forwarding when needed.
They can't call you at work or contact your employer. They are only allowed to call after a certain period after the previous call. If they violate the Fair Debt Collection Act, you can file a lawsuit against them and have the entire debt canceled. That's why it is wise to have an automatic call recorder on your phone, and a number of other reasons.
There’s an opt-in exception. This ruling is meaningful but not meaningful because companies do everything they can to maximize their freedom to share your contact information via fine print.
“I wonder now about my doctor, my dentist, my hospital and etc that have a robot call a day in advance to remind me of my appointment and sometimes leave a voice mail.”
Shouldn’t apply because you already have an established business relationship with them.
This is more for the cold calls IE “Hello we’ve been trying to contact you about your vehicles warranty.”, Or “You are now qualified for (insert scam here)”
“I wonder now about my doctor, my dentist, my hospital and etc that have a robot call a day in advance to remind me of my appointment and sometimes leave a voice mail.”
I believe those are fine as long as you have business with the caller.