Apple India — range problem

I bought an iphone 6 from saudi arabia. And i used it for 1.5years, suddenly it doesn’t show any range of my sim, then i changed the sim also it shows same as earlier. And i visited an i care centre in india they told me that their is a board complaint happened to my iphone, and they said to me they have no repair options they have to exchange with a new one of rs 27000/- i don’t have enough money like this. What i do for this problem? And the phone didn’t get much used by me, and i wondered how it happened?
I want a solution immediately because we are the customers of your product and you have the responsibility to take care us. Thank you