SONY XPERIA
Company is not replacing my cellphone

I have purchased a Sony Xperia Tipo ST21i2 at 16/11 that is till now I haven't completed 2 months. It is in silver color body dual sim.

Now,

In a very short period of time I am facing a very big problem that is Its silver color is going down white. Its a very serious issue I am facing.

I want to replace my cellphone and want a cellphone with black body as soon as possible because I have paid a very big amount for it but company is not replacing it.

Please help me...

Thanks.