I am also of the same opinion. Actually, I have been working with the bank for the last 6 months, and they never bothered to ask for a bond. Now, when I have served the notice, they are giving me nightmares.
Anyway, thanks for validating my thinking, but still, I am very worried... they may just hold my relieving letter. Can you please clarify one more thing?
In my offer letter, it says, "The bank can terminate your services by giving one month's notice during the probation period." It never mentions if I can also resign by giving one month's notice. I think it should be from either side. They are asking me to give 3 months' notice, which is applicable to confirmed employees. If there is any specific clause related to probationers, then that should be applicable as a general condition for the 3 months' notice.
Anyway, thanks for helping me.