  Temperature-dependent polarized Raman spectra of electron-doped
superconducting Pr$_x$Ca$_{1-x}$Fe$_2$As$_2$ ($x \approx 0.12$) single crystals
are reported. All four allowed by symmetry even-parity phonons are identified.
Phonon mode of B$_{1g}$ symmetry at 222 cm$^{-1}$, which is associated with the
c-axis motion of Fe ions, is found to exhibit an anomalous frequency hardening
at low temperatures, that signals non-vanishing electron-phonon coupling in the
superconducting state and implies that the superconducting gap magnitude
$2\Delta_c < 27$meV.
