I sent this company a message to their email address more than a month ago, asking them politely not to call my number again. My email transmitted (no bounce back) so there's no doubt HSUS received it.
Subsequently I've gotten a call from HSUS at this number nearly every day.
I am not an attorney nor a tax expert, but I would suggest you do some quick research on HSUS, pay particular attention to what percentage of donations to this "non-profit" actually reach the cause.
Also do not confuse HSUS with The Humane Society that does do such great work with cats and dogs in need of homes.