Have you followed the rules for submission of resignation?
Send a reminder and then raise the level so that your resignation gets accepted.
They cannot compel you to work for them
One suggestion: when you put a query at least stick to decent grammar and punctuation etc.
Here lot of working professionals would be seeing the query and poor presentation of query.
5th December 2017 From India, Pune
You have not given complete information. Every appointment letter carries an exit clause. If you want correct advice, please share the complete exit clause here then appropriate advice can be given.
6th December 2017 From India, Thane
6th December 2017 From India, Mumbai