Currently, the Avast call/sms filter does not allow you to enter a custom number with 3 digits to block. You must enter at least 4. So, if I was getting a lot of SPAM calls/sms from area code 214 for example, I would not be able to enter 214* to block all calls starting with that area code.
I propose that Avast allow us this functionality for those of us that get many SPAMs from the same area code. Many other call blockers allow this.