呼叫者是否知道我阻止了他们的电话？
in theory, no  though of course, they may get suspicious when you stop answering or returning their calls or if they can’t reach you.   
the caller won’t receive any sort of notification that their number has been blocked. 
instead, they will hear/receive messages saying that the number is no longer in service or that the text message couldn’t be delivered. 
一旦您阻止了一个来电者，他们将无法再与您联系，反之亦然，直到您取消阻止电话号码。
some businesses may wish to block their phone number from being displayed on the recipient’s caller id screen. this is especially common if companies are concerned that consumers will not answer their telephones if they see that the call is coming from a business.   
不te that it’s impossible to block your caller id when dialing 911, or if you are calling from a vanity (800) number. 
though we don’t recommend this, you may dial 67 before the phone number to have your caller id blocked, or change your settings, if available, to avoid showing caller id. 
if you do this, your caller id will appear as “unknown” or “anonymous”  which may not make the caller any more eager to pick up. 
it’s much better to choose a customized caller id.