I would rename your classes "Teller" and "Customer" because an object of those classes represents one teller or one customer. Then name your array "customers".
However, as Daved pointed out, your Inline class should contain the array. In addition, the Inline class will contain the methods to add customers to the array and keep track of how many customers there are in the array.
//assign a customer to the array:
customers = customer3;
You also need to be aware of what happens when you pass an object by value to a function vs. what happens when you pass an object by reference to a function. You always want to pass objects by reference to avoid copying.