Welsh was least likely to be offered or used when Welsh speakers had contacted the service using an email, letter or online form.
Roedd y Gymraeg leiaf tebygol o gael ei chynnig neu ei defnyddio pan oedd siaradwyr Cymraeg wedi cysylltu â'r gwasanaeth drwy e-bost, llythyr neu ffurflen ar-lein.