OnePlus India — product not working proper

Its a new device only 2 days used. Sometimes i get noticed by someone who tried to call me but he couldn't contact me.
When i'm trying to call him back i get a message "cellular network not available". But the strange thing is, that i can use cellular data without any problems same time. I can only call if i restart my phone manually or if i on and off airplane mode. Otherwise i cannot tell if someone is currently trying to call me and if he has issues getting me in touch. Its very annoying