hello
the basic pay is added to the grade pay. here although you joined in 2013, as per the pay protection rules, In cases of appointment of a Government servant to another post in Government on acceptance of technical resignation, Past service rendered by such a Government servant is taken into account for reckoning of the minimum period for grant of annual increment in the new post/ service/ cadre in Government . Pay of the substantive post held by the Government servant is protected. After Sixth Pay Commission, only the pay in the pay band is protected and the employee gets the grade pay of the post to which he is appointed after his resignation.
if the department is adamant and does not give you the pay, file a OA in the PRINCIPAL BENCH CAT, NEW DELHI.
REGARDS