1.
to be using the telephone :
He's been on the phone to Kate for more than an hour.
2.
( BrE ) to have a telephone in your home or place of work :
They're not on the phone at the holiday cottage.
BE ON THE PHONE
Meaning of BE ON THE PHONE in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005