Information sought on Resignation which was declined after 45 day

I resigned from a public sector bank on 23.01.2015 on getting a good offer from a private bank. I clearly mentioned in resignation letter that I be relieved by 31.01.2015 and that as I would not be able to serve notice period of 3 months, I am ready to surrender three months salary which I kept in my salary account. Bank officials told me to keep attending office and that my resignation would be accepted soon. In meantime private bank pressurized me to join immediately else they would not provide me the location of my choice. After attending office for exactly one month from the date of resignation and on realizing that the assurances given to me were false I stop attending the office from 24.02.2015 and joined the private bank from 27.02.2015. On 28.02.2015 a letter of unauthorized leave was sent to me which was received by my neighbor and given to me on 05.03.2015. Reply of this letter was sent to bank by me on 10th march 2015 (exactly 45 day from the date of resignation) reminding about my resignation and cc this letter to HO. Now the bank has declined my resignation through their letter dated 09.03.2015 which was posted by them on 12.03.2015 and received by my same neighbor and handed over to me by him on 13.03.2015. In the letter they stated that the loan proposals I recommended were faulty and that bank funds were jeopardized due to this (I was on probation during this time). My queries are as follow:- (1) Can a bank after 45 days from the date of my resignation decline my resignation, even though i hve clearly mentoned them to deduct 3 months salary? (2) Will this decline of letter have any impact on my job with private bank? (Private bank has exempted me of providing relieving letter) (3) Shall my resignation can be declined for the reason of work done in my probation period? (I was handling the branch operations too during this time period) (4) What shall I do now? k.t, Mohali, Punjab