Chargesheet and Resignation

I am working on clerical post in RMS (India Post). I joined the department on 14.3.2015. There was bond of 2 years probation period. I went absent and served resignation on 1.7 2016 they called upon me and asked to add few lines, so on 8.7.2017 they took another resignation from me. They sent me 2-3 notices since than, asking me to pay Rs.72804 as training expenses and one month pay..... But I withdrawn my resignation on 1.10.2017 and they allowed me to re-join on 21.10.2017. Counting that period as dies.non In the mean time I applied few exams without taking any NOC. Now, as I was doing duties from last 7 months, apparently one of my exams got cleared and I served resignation with immediate effect on 2.6.2017 but they rejected my resignation saying that there is no such ruling for immediate resignation and asked me to continue duty. I did duties for 2.3 days and on 5.6.2017 I resigned with 24 hours notice Now they applied charge sheet against me regarding that absence period 1.7.2016 to 20.10.2016...... And not accepting my resignation I already joined other department on 7.6.2017 withour telling either of the departments. Kindly suggest me what to do ....?