Single-frame off-axis holographic reconstruction is promising for quantitative phase imaging. However, reconstruction accuracy and contrast are degraded by noise, frequency spectrum overlap of the interferogram, severe phase distortion, etc. In this work, we propose an iterative single-frame complex wave retrieval based on an explicit model of object and reference waves. We also develop a phase restoration algorithm that does not resort to phase unwrapping. Both simulation and real experiments demonstrate higher accuracy and robustness compared to state-of-the-art methods, for both complex wave estimation and phase reconstruction. Importantly, the allowed bandwidth for the object wave is significantly improved in realistic experimental conditions (similar amplitudes for object and reference waves), which makes it attractive for large field-of-view and high-resolution imaging applications.