There is a difference between "Being of Service" and "being a servant". To Be of Service means that you're joyfully giving according to your ability and what you are giving comes from the heart. Being a servant means that you're giving or doing out of obligation. Also keep in mind that doing for someone who doesn't want or need you to is not service, it is a form of control.
To notice a need and step forward assist, be of service. This is done no matter if noticed, thanked, appreciated, recognized or not. The service being great, it's done still. It's unconditional and done with care and love. I do simply because. .