YOU SAID:

I have no idea how to get him away from his phone

INTO JAPANESE

私は彼を彼の携帯電話から離れる方法がわかりません

BACK INTO ENGLISH

I don't know how to get him away from his cell phone.

INTO JAPANESE

私は彼を携帯電話から離す方法を知らない。

BACK INTO ENGLISH

I don't know how to get him off his cell phone.

INTO JAPANESE

私は彼を携帯電話から降ろす方法を知らない。

BACK INTO ENGLISH

I don't know how to get him off his cell phone.