If you *67 your phone number, how does someone get the number you called from?

I've blocked my number. and this person still manages to call me back on my number. I changed the number , block my number and still get called.If you *67 your phone number, how does someone get the number you called from?Why do you keep calling a number that obviously does not want your calls. The person probably guesses that it is you calling, and calls you back, even though you block the call. I hope you are not a stalker.