Big vouch for Xcaller and the support team (or one guy, unsure).
I bought it a week or so ago with the intentions of running it on a new MBP and the Monterey OS Update was coming (now out). Apple's are a pain in the ass with their restrictions but Timo spent literally a handful of hours over multiple days digging with me to make it work. Ultimately he of course figured it out and got it working after a few looks. I was impressed. He also assured me beforehand that a refund would be guaranteed if he could not get it to work.
I have been using it quite a bit in the last couple days and it works flawlessly. It's been great to fuck around with people, spoof a number for SE and other uses so far. I am happy with the product and would recommend it to anyone looking for a call spoofer.
The spammer also works pretty well, have not tried the other functions but will update when I get around to it.
10/10 Product
10/10 Support