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The Effective Field Theory (EFT) approach is widely used in the search for possible deviations from the predictions of the Standard Model. Such an approximation of possible BSM physics is valid up to a certain levels of energy scale and accuracy. In this article, we investigate potential limitation of the EFT approach related to unitarity to describe possible contributions of flavor changing neutral currents (FCNC) involving the top quark. The numerical and analytical calculations of the FCNC processes used in the EFT approach demonstrate the constant asymptotic behavior of the total cross section with increasing energy. It is shown that the EFT approach for studying the possible contribution of FCNC does not violate the restrictions following from perturbative unitarity, the asymptotic behavior of the cross section does not exceed the Froissart bound, and the approach itself can be used to set the corresponding experimental limits for FCNC couplings or Wilson coefficients at present and future colliders.