Spy Dialer's privacy notice offers two ways to opt out of the sale and sharing of your information, the web form and a phone call to (866) 834-2579. The same number sits on the company's California data broker registration, so it's the line the operator itself nominated for exactly this. We haven't placed a removal call ourselves, so we can't say how the call goes or how long a block takes.
Have ready the four things the wizard would have asked for, your name, your address, your phone number and your email. On a phone-lookup site the number is the entry that matters most, so give every number you've held, not only the current one. Ask for the details to be blocked from future sharing, which is the wording the wizard's own success screen uses, and note the date and who you spoke to.
If you'd rather write, the registry lists info@spydialer.com as the company's contact and the privacy notice gives support@spydialer.com. Neither is described as an opt-out channel, so treat email as a paper trail beside the call rather than a substitute for it.