Is it permissible to change the name of one's deceased father, if his name was "Abd al-Nabi" (Slave of the Prophet) or among names that are impermissible in Sharia or socially unaccepted, to a better name?

Changing disliked names is permissible. The Prophet, peace and blessings be upon him, changed some names of individuals and their fathers, such as changing "Ghawī ibn 'Abd al-'Uzzā" to "Rāshid ibn 'Abd Rabbih." As for the names of the deceased, changing them is not necessary, because mentioning them by their original names makes it easier to identify who is being referred to.