Could you please implement a Python program that simulates basic bank account operations? The program should include the following features: 1. A function to create a new customer account if it doesn't already exist. 2. A function to deposit money into an existing account and return the total balance; if the account doesn't exist, the function should return None. 3. A function to process payments by deducting the amount from the customer's balance, but only if sufficient funds are available. If the balance is insufficient, the function should return a message indicating so. If the account doesn't exist, it should return None. Each account should be identified by the customer's name, and the program should handle multiple customers.