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.  Once you block a caller, they will no longer be able to contact you, and vice versa, until you unblock the phone number.