Unpaid salary

Though you do not have appointment letter, but your salary slip is more than enough to prove your employment. 

However, coming to the point of recovery of wages, since you have already served a 'gentle' notice, you are now required to claim legally through courts depending on the nature of nature of establshment. 

For further advice, you should consult a lawyer. 

You may claim that while appointing you by verbal order you were always assured that appointment letter shall be issued to you and NO Notice Period for resignatin shall be applicable in your case.

You are covered by the Payment of Wages Act that dos not discriminate between 'Workman' and 'Non Workman'. It is mandatory to supply the salary/pay/wage slip and maintain record for 3 years (Sec;13A). Hence you may demand all of these and also service certificate.

Lodge complaint under this Act with Inspector appointed under this Act.

Contact O/o Labor Commissioner.

You can seel counsel of an able counsel specializing in labor-service matter, and support from unions.