Sansui India — no updates received on my phone since purchase

Its almost a year now and till date i've not recieved any form o[censored]pdate on my phone which is now lagging crazily and showing flaws unimaginable. Push advertisements, security breach, bitcoin mining (Minebot), all these are happening inside my phone now and the reason i assume is lack o[censored]pdates. Its currently running android 4.4.2 _ph model u45. Thereby i request the one in-charge to provide the latest software update atleast upto 1.5 years maximum because this phone is still too young to get outdated. Please provide satisfactory customer care. Thank you