reinstatement to govt duty after relievef by voluntary retitedment

sir I have retired from service on 30.11.2017 fore noon as postal assistsnt in the post dept visakhapatnam andhra due to cancer treatment .some what cured now can i have any chance to get my job .i have received the commutation gratuity pf amount etc. i have applied reinstatement to duty on 21.2.18 the same was rejected.as resignation. and voluntary is different.kindly clarify whether I can have any chance to get my job by constititoonal provision please help my murali retired postal asst visakhapatnam 9290016534 watts up 8338590094