I don't think theres a built-in blacklist feature on the Ace, but you could install blacklist apps like Calls Blacklist.
LINK HERE: https
/play.google.com/store/apps/details?id=com.vladlee.easyblacklist&feature=search_result#?t=W251bGwsMSwxLDEsImNvbS52bGFkbGVlLmVhc3libGFja2xpc3QiXQ..