Calleja is a surname found in Spain (as well as countries people of Hispanic descent) and Malta. It is unclear Maltese and Spanish surnames are related or a coincidence, perhaps caused by romanization—a Surname DNA project exists with the one of its stated goals to determine if there is a relationship.
Read more about Calleja: Variations, Spain, Malta, Calleja/Calleia/Calleya/Callea DNA Surname Project, Calleja May Refer To