This wording has been used by other freelance Virtual Assistants to great success:
"Welcome to Time etc.
My name is XXX and I have been matched up and assigned to assist you with any tasks that you need completed through Time etc.
I would like to set up a call with you so we can go over your needs and expectations, and I can tell you a little bit more about myself and how I can help you.
Please let me know what would be the best time to speak? I can call you, or you can call me on xxxx
I look forward to working with you