I have found that spam callers are now using software that makes the return number prefix the same as the number being called.  That way you might think it's someone you know.  But my basic rule is that if the person is unknown to me and does not leave a message they go directly to the auto-reject list.  This one is in this category.  After you list is full (usually 100 numbers) you can delete them from the first one you entered forward.   That means the oldest one gets removed from the list first.