RSVP search tool showing half-matches

Others have posted about similar problems, but I am having trouble with the RSVP function on our wedding website. Previously, when a guest typed in their first and last name only their name (and any 'linked' guest's name, as in a couple or family) would appear. However, it now seems that all guests with the same last name appear in the search result, regardless of whether the first name matches. As we have many guests with the same last name, this makes both us and our guests uncomfortable and it seems unnecessary. There doesn't seem to be a point in making the guest input both first and last name if the result shows everyone that matches even just one of the two fields. Is there any way to have the search come back with exact matches only? Thanks in advance.