Is it permissible to converse with one's fiancée via the internet or phone, and what are the limits of such communication, given that both families are aware of the situation?

The suitor is a stranger to the fiancée until the marriage contract is concluded. He is to be treated like any other strange man. It is not permissible for him to speak with her or chat with her except out of necessity and without softness in speech. The fiancée is like any other non-fiancée in the prohibition of looking at her, being in seclusion with her, and speaking to her, except for the permissible gaze for the purpose of engagement.

Ibn Uthaymeen said: If the suitor wishes to enjoy sitting and speaking with his fiancée, then let him conclude the marriage contract, for the contract makes permissible for him everything that is permissible for a husband with his wife. As for being alone with the fiancée and making excuses about commitment, this is from the deception and delusion of Satan, for Satan flows through the son of Adam like blood, especially with his fiancée, who will soon become permissible for him.

Therefore, it is forbidden for the suitor to speak with his fiancée on the phone, or to be in seclusion with her, or to give her a ride alone in his car, or for her to sit with him and his family while her face is uncovered.