Apple India — Iphone 6s showing error on using all the time

Address: 110059

My phone is not supporting whatsapp, gmail... It's been only 6 months by purchasing this but this is not working properly from the very first day.. Everyday i need to reset my network settings as your executive suggests this to do. But who does that and what is the point in getting 45000 phone for doing this only. Everytime i'm unable to receive my call then by touching speaker button on and off then i'll able to get any call.