...and the recipient is receiving your tel number in the caller ID, despite you having the blocking turned on?
Yes, my Sonic number (Mtn. View) shows up at the Sonic recipient's phone (San Jose) when I enable Caller ID Blocking via the member tools. With blocking enabled, calls to my Verizon Wireless cellphone show the caller as "Restricted", no number is available.
Caller ID blocking also fails between me (Mtn. View) and a Sonic member in San Francisco.
I have subsequently disabled that blocking. Advise if you need any more details.