Need help about replace a nokia handset due to fault in battery ?

I have bought a nokia e4 handset from a nearest planet M shop on before 2 months. But this new handset giving me lots of problems coz of fault in battery. When I reached to Nokia car center to replace the handset they said the battery no. should be written on the bill which is not written on bill but when I contact to the shopkeeper from where I bought the handset they reply me that there is no need of that. Now i am so confused what should i do guyz plz help ??