What is the ruling on practicing phone sex with one's fiancé after the marriage contract but before the wedding, and what is the ruling on going out with him without the family's knowledge?

If a lawful marriage contract has been concluded, then it is permissible for the husband to discuss sexual matters with his wife. However, doing so online is fraught with risks, and there is no guarantee that someone else won't see it. This action may increase sexual arousal rather than quell it, and exposes one to temptation and harm. You are not obligated to obey him in this matter, nor in his request for khalwah (private seclusion) with you before consummation, as a woman's obedience is to her father as long as she is in his home. We advise you to gently counsel your husband to desist from this matter, to be keen on chastity, to avoid anything that incites lust, and to hasten the completion of the marriage.