Most Probably this company shall be covered by (Name of the state) Shops and Commercial Establishments Act.............................and standing Orders might also apply to it.........................
Notice period is part of service conditions and the above being enactments/instrument of law/statue shall prevail upon any private agreement/policy that employer has crafted/drafted be it e.g. offer letter/appointment letter/HR policy etc......................even if these are 30 pages of even 3000 pages long.............................and employer is personally held responsible for faithful observance of enactments applicable to the establishment.................and service conditions that are violative of enactments shall not survive.......
(Name of the state) Shops and Commercial Establishments Act: As per it the notice period for length of service of 3 months.......................may be NIL, hence not notice period and notice pay in lieu of notice period might apply to you (employee).....
Standing Orders: are certified on the lines of model standing orders.If not certified model standing orders shall apply. Notice period during probation period is NIL.....
The notice period has to be honored by employer....
Approach your able Labor Law consultant/Service lawyer with confidence..