In this passage the preposition upon was accidentally replaced by the preposition on in the 1874 RLDS edition. The 1908 RLDS edition restored the original upon. Either reading is theoretically possible for the phrase “to call (up)on God”, or its equivalent; in the earliest text, there are eight instances with upon and two with on. On the other hand, when the phrase is “to call (up)on the name of God”, or its equivalent, there are five instances with upon and ten with on. In each case, we follow the earliest reading, thus upon here in Mormon 5:2.
Summary: Maintain the preposition upon in Mormon 5:2 (“without calling upon that Being who had created them”).