No form has to be filled for u to get your call-up letter.If you have cleared the written exam and your roll no. Is in the list, then sooner or later you will get your call-up letter.I would suggest you to keep looking for your SSB dates. Online on sites like Join Indian Army. Because the hard copy may be delayed due to postal errors or faults.Just to reassure you, NO FORM HAS TO BE FILLED TO GET YOUR SSB CALLUP LETTER.Cheers and All the Best