AO Smith — Once i call, either service engineer assigned doesn't pick up the phone or i get some false commitments of visits

Hi, i have registered my service request[protected] on 30th april when my x4 water purified stopped working suddenly. Though my purifier is under complete amc for 2 years, none has visited it in almost 2 months time. Once i call, either service engineer assigned doesn't pick up the phone or i get some false commitments of visits. After repetitive requests, i am now become frustrated and even don't feel to call them again to get another false date.

Please help.
Regards,
Ranjan