Sed contra: "For the ordering of His future works in His foreknowledge, which cannot be deceived and changed, is absolute, and is nothing but, predestination ... Why are they not afraid that exhortation to these other things, and the preaching of these other things, should be hindered by the definition of predestination? Or, perchance, do they say that such things are not predestinated? Then they are not given by God, or He has not known that He would give them. Because, if they are both given, and He foreknew that He would give them, certainly He predestinated them. ... That is, therefore, He predestinated them; for without doubt He foreknew if He predestinated; but to have predestinated is to have foreknown that which He should do." (On the Predestination of the Saints, II:41-2, 47).
Now, if what you say is true, that Augustine denies that "man somehow makes a choice to choose God or reject God," then what do you make of his words, for he himself writes as follows: "And thus, when it is said, 'For who maketh thee to differ? and what hast thou that thou receivedst not?' if any one dare to say, 'I have faith of myself, I did not, therefore, receive it,' he directly contradicts this most manifest truth,--not because it is not in the choice of man's will to believe or not to believe, but because in the elect the will is prepared by the Lord" (On the Predestination of the Saints, I:5). Doesn't Augustine clearly reject the opinion that "it is not in the choice of man's will to believe or not to believe," and isn't it this same opinion that you've just ascribed to him? What Augustine affirms here, and here the Church has added her voice to his, is that only those who predestinated by God are moved to believe by his grace which "precedes, prepares and elicits our free response" (Compendium of the Catechism of the Catholic Church, §425).
You quote from Calvin as follows: "Ought we not then to be silent about free-will, and good intentions, and fancied preparations, and merits, and satisfactions?" Yet Augustine was not silent about any of these things, and I could give very many examples of him writing and speaking about merits and satisfactions, free-will and good will, and preparations for grace (these preparations, of course, are from God also).
Although I've searched for this passage and can't find it. Off hand, if he did state it, I would say your misinterpreting his words. Here is some of Augustine's views on foreknowledge which can be found in A Treatise on the Predestination of the Saints
Further, between grace and predestination there is only this difference, that predestination is the preparation for grace, while grace is the donation itself. When, therefore, the apostle says," Not of works, lest any man should boast. For we are His workmanship, created in Christ Jesus in good works," [Eph. 2.9,10.] it is grace; but what follows—"which God hath prepared that we should walk in them"—is predestination, which cannot exist without foreknowledge, although foreknowledge may exist without predestination; because God foreknew by predestination those things which He was about to do, whence it was said, "He made those things that shall be." [Isa. 46.11.]
And assuredly, if this were said because God foreknew that they would believe, not because He Himself would make them believers, the Son is speaking against such a foreknowledge as that when He says, "Ye have not chosen me, but I have chosen you;" when God should rather have foreknown this very thing, that they themselves would have chosen Him, so that they might deserve to be chosen by Him.
"Therefore," says the [sic:heretic] Pelagian, "He foreknew who would be holy and immaculate by the choice of free will, and on that account elected them before the foundation of the world in that same foreknowledge of His in which He foreknew that they would be such. Therefore He elected them," says he, "before they existed, predestinating them to be children whom He foreknew to be holy and immaculate.
For they think that "having received God's commands we are of ourselves by the choice of our free will made holy and immaculate in His sight in love; and since God foresaw that this would be the case," they say, "He therefore chose and predestinated us in Christ before the foundation of the world." Although the apostle says that it was not because He foreknew that we should be such, but in order that we might be such by the same election of His grace, by which He showed us favour in His beloved Son.