Does the husband deserve the full mahr if he wishes to divorce his wife after consummating the marriage but before the wedding, especially if she cheated on him through phone calls?

A man owns his wife as soon as the marriage contract is concluded, and everything permissible for a husband with his wife becomes permissible for him. However, he should observe the prevailing custom and the agreement made with the woman's guardian. If intercourse or a lawful seclusion occurs, there is no sin upon him, and all the rulings of consummation apply thereafter, such as the entitlement to the full dowry. If the husband is certain of his wife's infidelity via phone, and she does not regret or repent, it is better for him to divorce her honorably, inform her family of his consummation with her, and pay her the remainder of her dowry, especially if she was a virgin and became non-virgin because of him, in order to avoid accusing her unjustly.

The husband is not permitted to reclaim the dowry due to the wife's infidelity, as the dowry is fully established by seclusion, physical contact, intercourse, or death. The woman's infidelity does not justify the husband seizing her dowry, even if the case reaches Li'an (oath of condemnation) or admission of adultery. The dowry is a right for the wife for what the husband has made lawful of her private parts.

What the husband can do is put pressure on the wife to relinquish her dowry and ransom herself, in accordance with the verse: ﴿وَلا تَعْضُلُوهُنَّ لِتَذْهَبُوا بِبَعْضِ مَا آتَيْتُمُوهُنَّ إِلَّا أَنْ يَأْتِينَ بِفَاحِشَةٍ مُبَيِّنَةٍ﴾ (An-Nisa: 19) "And do not make difficulties for them in order to take part of what you have given them, unless they commit a clear immorality." So, if the wife commits a clear immorality, such as adultery or defiance (nushuz), the husband is permitted to make difficulties for her as a punishment for her to ransom herself. And phone infidelity is sufficient to permit putting pressure on her to relinquish her dowry.