How do we know the early Church believed and worshiped this way? It is of interest to note that the word "altar" is used over 545 times in the writings of the Early Church Fathers before the end of the 6th century? Saint Augustine used the term over 149 times alone and the most ancient Liturgy of Saint James uses the word 36 times. This liturgy records the words of the celebrant praying to God to change the bread and wine into the body and blood of Christ. A little hard to claim transubstantiation was from the 12th century with that! But alas, if there was no sacrifice in early Christian worship as our Protestant brethren maintain, why would there be altars and sacrifice mentioned repeatedly? (Incidentally, the word "call" never followed the word "altar" in any of my research, but I digress.)
PROTESTANT EARLY CHURCH HISTORIAN J. N. D. KELLY writes that in the early Church "the Eucharist was regarded as the distinctively Christian sacrifice.... Malachi's prediction (1:10-11) that the Lord would reject Jewish sacrifices and instead would have "a pure offering" made to him by the Gentiles in every place was seized upon by Christians as a prophecy of the Eucharist. The Didache indeed actually applies the term "thusia," or sacrifice, to the Eucharist.... "It was natural for early Christians to think of the Eucharist as a sacrifice. The fulfillment of prophecy demanded a solemn Christian offering, and the rite itself was wrapped in the sacrificial atmosphere with which our Lord invested the Last Supper. The words of institution, 'Do this' (touto poieite), must have been charged with sacrificial overtones for second-century ears; Justin at any rate understood them to mean, 'Offer this.'... The bread and wine, moreover, are offered 'for a memorial (eis anamnasin) of the passion,' a phrase which in view of his identification of them with the Lord's body and blood implies much more than an act of purely spiritual recollection" (J. N. D. Kelly, Early Christian Doctrines [Full Reference], 196-7).
"IN THE "SACRAMENT HE IS IMMOLATED "FOR THE PEOPLE NOT ONLY ON EVERY EASTER SOLEMNITY BUT ON EVERY DAY; AND A MAN WOULD NOT BE LYING IF, WHEN ASKED, HE WERE TO REPLY THAT CHRIST IS BEING IMMOLATED. FOR IF SACRAMENTS HAD NOT A LIKENESS TO THOSE THINGS OF WHICH THEY ARE SACRAMENTS, THEY WOULD NOT BE SACRAMENTS AT ALL; AND THEY GENERALLY TAKE THE NAMES OF THOSE SAME THINGS BY REASON OF THIS LIKENESS" (LETTERS 98:9 [A.D. 412]). ST. AUGUSTINE