Amul / Gcmmf — complaint about amul milk product

I bought 2 half packets of amul full cream milk for making rasgulla. I boiled it and after giving it rest for some minutes i added a pinch of tartaric acid to make it chenna. But the milk remains the same and it didn't become curdled. I tried so many times by putting lemon juice also, but all was in vain. Finally i got tired of repeating this and compiling against it. I think the milk is not appropriate otherwise milk is such a sensitive liquid which instantly get curdled if even comes in a contact with lemon or salt or tartaric acid. Please tell why this happened with your product as i used so many milks of other companies but got a satisfied result.
Thankyou
Regards