What is the ruling on calling someone whose ringtone is a song, and does the ruling differ based on the time of the call (prayer time or otherwise) or on whether the matter is urgent, and what is the limit of urgency?

It is permissible to call someone whose phone ringtone is music out of necessity or need, provided that the caller does not intend to listen to the music. The caller must advise them to change the ringtone. Some scholars believe it is impermissible to call someone whose phone ringtone is music to avoid falling into sin, except out of necessity. However, there is no sin upon one who does not know about the prohibited ringtone. If there is a need or necessity to call someone whose phone ringtone is music, there is no blame on the caller. But if the call is out of curiosity, it is better to avoid it. It is not advisable to call a person known to be praying, whether their phone ringtone is music or not, as this distracts and disturbs the worshipper, especially if they are praying in the mosque, as it harms other worshippers and violates the sanctity of the mosque.