I'm not sure a month would be long enough. Not even a year. But I also think that customers with an issue are not really at fault. It's really the fault of the way that companies have approached the call center. When someone calls with a complaint, it's always the last option in a long list of menus.
Just yesterday I had an experience with one, and I wasn't calling to make a complaint, I was calling to give kudos to someone who had done an exceptional job. By the time I found the right menu in the most dickweed call center options, 5 full minutes had passed, and I felt frustrated. Way to go. But I persisted. In the end, I made the comment about the fellow who helped me, because he deserved it. Then I filled out the survey they sent via email, I was not all that generous. About 15 minutes later, I got an automated email reply. "We're sorry about your experience, we're here to help. Please fill out this form...". Honestly what I read in that email quickly turned into "blah blah blah".
That is when I got angry.
Who did this? My own employer, that's who. I was calling to give kudos to an exceptional young man who had helped me deal with a disability accommodation request I had. The people who design these systems are probably well meaning, smart individuals. But they have no idea what it's like to deal with their system. And we use the same system for client facing call centers. Way to go.
My advice to anyone developing automated systems, or software, and this also includes CIG because they don't get it either. Make sure the HELP menu in your menu options is not buried. Make it an option at every level. In the help options, don't assume you know all the choices the client might have. This is easy to do. I can go on with a really long list, but that's not productive. Instead, I say something like this: "Just pretend the person selecting the help options is your grandmother or mother. Now, how would you approach it?"