Dell - my battery drying

Dear Sir Madam I bought Dell Inspiring Laptop Tag DBF**** on ** July ****.And I bought an Additional warranty for * years and I paid extra amount also. So the concern is my battery drying very Fast so this reason I called Dell India Ltd so they simply denying my concern till I have warranty NBD Next Business Day Service I read that document clearly and sent that document to Dell and his saying the same thing what is the advantages of paying extra amount. they simply denying the battery carry only * year warranty from the date of invoice. this is normal *-year warranty given by any company .why he collected for extra amount need clarification about this thing.