Number keypad during automated phone call directory (IE "for customer service, press 1") DOES NOT WORK.

I have an iPhone XR and cannot choose a response for automated phone menus; they do not recognize my entries. For example, "press 0 for the operator", and I push 0 numerous times and get a message that the system does not recognize my entry and continues to tell me to make a choice. This problem has happened on several different automated systems. Pleas Help!