Siman 595

A person who is unable to blow the shofar himself, nor to recite the blessings himself, and there are two places before him: in one they blow but do not recite the blessings, for there is no one there who knows how to recite these blessings of Malchuyot, Zichronot, and Shofrot; and in one place there are those who recite the blessings, but there is no shofar there or there is no one there who knows how to blow—it is obvious that he goes to the place where they blow, and not to the place where they recite the blessings. For the blowings are from the Torah, and the blessings are from the rabbis.

And not only that, but even if the shofar blasts are in doubt and the blessings are certain—he should go to the place of the shofar blasts, for a doubt regarding a Torah commandment is more stringent than a certainty regarding a rabbinic commandment. And it is a simple matter that if he can go to a place where they pray and there will still remain time in the day to go to the place of the shofar—that he is obligated to go first to the place of prayer, even though it is rabbinic, because afterward the individual will not be able to pray for himself, which is not the case regarding the shofar blasts, as I wrote in the previous siman. And it has already been explained in siman 586 that the shofar does not override a shevut. And only by means of a non-Jew, which is a shevut d'shevut in the context of a mitzvah—is it permitted (see Magen Avraham, subsection 2).