“How was Saul able to call Samuel through the witch of Endor? “
God doesn’t want us accessing departed souls through witches.
The issue is not the use of witches but the ability of the dead to hear the pleas of the living. Scriptures says they can. No witches are involved.
Not only that but Samuel was pretty ticked off about being disturbed - NOT the kind of attitude expected of one who is "supposed" to be available 24/7 for "intercession". Also, Saul lost his kingdom and, eventually, his life for this disobedient act. Going to the dead was against God's command - one He NEVER rescinded.