International Journal of Innovation Scientific Research and Review Vol 03, Issue, 11, pp 1945 1949, November, 2021 Available online at http //www journalijisr com SJIF Impact Factor 4 95 Research Article ISSN 2582 6131 COMPLAINTS A FACTOR OF THE LOYALTY * Thi Le Ha Nguyen University of Medicine and Pharmacy, Vietnam National University, 144 Xuan Thuy, CauGiay, Hanoi City, Vietnam Received 10th September 2021; Accepted 13th October 2021; Published online 20th November 2021 ABSTRACT The present pa[.]