I guess it depends on the jurisdiction, but in Europe (at least, France and Italy I'm certain of) the phone number is treated as personal sensitive data[1] and

I guess it depends on the jurisdiction, but in Europe (at least, France and Italy I'm certain of) the phone number is treated as personal sensitive data[1] and "owned" by the contract owner, not the telco. [1] https://commission.europa.eu/law/law-topic/data-protection/reform/rules-business-and-organisations/legal-grounds-processing-data/sensitive-data/what-personal-data-considered-sensitive_en https://commission.europa.eu/law/law-topic/data-protection/r...