How to block a no caller ID that rings u at least 20 times a dayon iPhone

An option that I use is Settings > Phone > Silence Unknown Callers. It silences all calls from sources not in your Contacts. See: Detect and block spam phone calls - Apple Support

You can do Settings > Phone > Silence Unknown Callers.

You could also work with your cellular carrier to have your phone number set up to require Caller ID.

I also have Silence Unknown Callers set and it works a treat. I also have recorded a greeting message that says

"If you are not in my contacts I will not get the call so make sure you leave a message"

because I have been known to miss calls from my doctor or bank because they use a withheld number. That is their problem.

coral38 wrote:

Thank you if this doesn[‘]t stop what would i have to do

Huh? Silence Unknown Callers has completely predictable behavior. If it fails to do what it’s purported to do (impossible), contact Apple.

If your cellular carrier can’t provide the remedy you’re seeking, consider changing carriers.