This code system http://terminology.hl7.org/CodeSystem/communication-not-done-reason defines the following codes:

CodeDisplayDefinition
unknown UnknownThe communication was not done due to an unknown reason.
system-error System ErrorThe communication was not done due to a system error.
invalid-phone-number Invalid Phone NumberThe communication was not done due to an invalid phone number.
recipient-unavailable Recipient UnavailableThe communication was not done due to the recipient being unavailable.
family-objection Family ObjectionThe communication was not done due to a family objection.
patient-objection Patient ObjectionThe communication was not done due to a patient objection.
 <status value="draft"/> <experimental value="false"/> <date value="2020-04-09T21:10:28+00:00"/> <publisher value="HL7 (FHIR Project)"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> <telecom> <system value="email"/> <value value="fhir@lists.hl7.org"/> </telecom> </contact> <description value="Codes for the reason why a communication did not happen."/> <caseSensitive value="true"/> <valueSet value="http://terminology.hl7.org/ValueSet/communication-not-done-reason"/> <content value="complete"/> <concept> <code value="unknown"/> <display value="Unknown"/> <definition value="The communication was not done due to an unknown reason."/> </concept> <concept> <code value="system-error"/> <display value="System Error"/> <definition value="The communication was not done due to a system error."/> </concept> <concept> <code value="invalid-phone-number"/> <display value="Invalid Phone Number"/> <definition value="The communication was not done due to an invalid phone number."/> </concept> <concept> <code value="recipient-unavailable"/> <display value="Recipient Unavailable"/> <definition value="The communication was not done due to the recipient being unavailable."/> </concept> <concept> <code value="family-objection"/> <display value="Family Objection"/> <definition value="The communication was not done due to a family objection."/> </concept> <concept> <code value="patient-objection"/> <display value="Patient Objection"/> <definition value="The communication was not done due to a patient objection."/> </concept> </CodeSystem>