Certain numbers don't ring but all others do

I have an iPhone 11 ProMax. Over the last few months certain phone numbers do not ring. Even ones in my contact list. It's somewhat of a hassle when a company or person I want to talk to just goes to voicemail. If I don't recognize the # I let it go to voicemail if the phone rings. Under settings silence unknown callers is off and the phone numbers are not blocked. Any help would be appreciated.