Duravit India — cracked wc

I purchased architect wc 3-4 years ago, it has got huge cracks and is broken on its own, i contacted the company, they are asking for invoice which i don’t have, they are now not ready to do anything, i didn’t expect a company such old will be having such cheap, disgusting product and after sales service. I want the company to correct it asap, the service agent said that it is very risky to use it, so i want the company to correct it immediately, the company can’t refuse to change the defective product due to lack of invoice,