Malwarebytes does Nothing to block calls by itself unless you list in the App the call numbers you wish blocked. However, there is an App "AT&T Call Protect" I find incredible. It self identifies and auto blocks telemarketers. spam risk calls, fraud calls and much more. You can decide if you want them totally booked or change the settings by call type to allow them to go to your v-mail. I find, as a Premium member of Malwarebytes for several years, that the product is useless both on scanning my computer and useless on my phone. It does Nothing.
I would try AT&T Call Protect. I like others feel that people that who are blocked by the Call Protect app. will leave a v-mail for me if they are legit. Call Protect works incredibly accurately and well for me. It also maintains a list of phone number blocked for you to validate or review. After many years, Malwarebytes I find a waste of time and money. And "yes" Apple also recommended Malwarebytes to me for a past Safari issue... but it has identified nothing since.