I'm not really sure what to say... I'm glad that your client is identifying you properly but I'm sorry that others don't seem to be respecting your wishes. Are your colleagues identifying you properly or choosing to let old habits linger? If they shift and are consistent then it might help to change the responses of the clients who will hopefully begin to respect your changes. I'm not a very pushy person so I'm the type to search for allies wherever I can find them. Maybe you can get a few people at a time to make the positive change and work constructively with the others and management to help the rest along the way. I'm sure others will have some helpful advice for you.
Until then, I wish you much peace.