Hi Jamie,
Question, are you the branch manager or trainer? If so, you have a little more opportunity to enforce the standards. When you see someone neglect to greet a customer, either call the person over (without making a big deal about it) or go to them and ask them why they didn't greet the customer? Did they forget or did they just not feel like it today? If you do this a couple of times, the word will spread like wildfire at breaks and lunch and by phone and email. Although they may think you are being bossy at first, you are, it's your job. It is a whole lot easier to train employees to do things right than it is to find new customers because they get treated better at another location.
If your team won't cooperate, even after training, it is probably time to review the mission statement and core values with them (hopefully your company has them and they are posted where staff can see them) and then if they still won't cooperate, replace them. One bad employee attitude can destroy the culture of the whole if they are left to fester, don't corrupt the whole because of one employee...
Good luck and if you need any other ideas you may want to go to the website
www.joyoftraining.com and get the ebook, lots of ideas that may help you in this situation and others.