How to calculate the low(high)-frequency dielectric constant correctly? about amset

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The calculation of the static dielectric constant depends on many factors, including DFT functional, energy cut-off, k-point mesh, initial force conversion criteria, energy conversion criteria, FFT mesh density, etc.

For the polar optical phonon frequency we take the highest energy optical phonon frequency at the Gamma point, taken either from a DFPT calculation or from phonopy.

You can calculate the high-frequency dielectric constant using the LOPTICS tag in VASP. Note for accurate values, often a hybrid functional is needed and the calculation needs many empty bands (generally, you should converge the high-frequency dielectric with respect to number of bands).