Trigger on contact object when i change account name

try below code and let me know if it doesn't work

trigger updateRelatedRecords on Contact (before update) {
    List<Case> caseList = new List<Case>();
    List<Task> taskList = new List<Task>();
    for(Contact con: trigger.new){
        Contact con1 = trigger.old[0];
        if(con1.AccountId != con.AccountId){
            Task newTask = [Select Id from Task where WhoId =: con.Id limit 1];
            newTask.WhatId = con.AccountId;
            Case newCase = [Select Id from Case where ContactId =: con.Id limit 1];
            newCase.AccountId = con.AccountId;
            taskList.add(newTask);
            caseList.add(newCase);
        }
    }
    update taskList;
    update caseList;
}