First of all I find the term telephone meeting a bit daft. To me a meeting is where two or more people get together to discuss business etc. I prefer the term telephone conversation, but I am bit old fashioned!
Anyway, this is how I would word it:
Dear xxxxxx, I hope you are well. Would it be possible for us to speak today at 3:00pm? If this is not convenient, please let me know a more suitable day and time.
I look forward to hearing from you,
Kind regards,
xxxxx
I would never begin an E-mail to client with Hello.