Resignation without serving notice period

Dear Experts,
I have resigned from a company due to many personal and professional reasons without serving the notice period. Let me point out the details:
1. After the interviews, I got an email stating the salary and all but there is nothing mentioned about the notice period or any bond.
2.But to my surprise, at the time of the joining, they signed me the offer letter, which has a clause that "I have to stay there for minimum 1 year" and there was nothing mentioned in case of a breach.
3.In the offer letter, there is nothing related to the notice period, the only mention is I will be on probation for 6 months. (But I think there might be some points related to the notice period in the company manual )
4.I put resignation from my personal mail id after intimating to my managers and never missed to reply any calls or emails.
But now, I got a legal notice that I have to pay them a huge amount of compensation and mentioned that I have absconded from the employment. I only worked with them for 2 months and told them to take the 18 days salary (LFS).
Are there any legal issues with my case? I have sent a reply to their notice.

there is no legal bond stating that the employee has to work for minimum 1 yrs in any organisation. furthermore, why are there are asking any compensation for 2 months? have they provided any specific training which they have invested in you?

Thanks, Moses, no they didn't provide me with any corporate training. Only thing happened was a client visit who explained about their infrastructure to the entire team (4 members) for 5 or 6 days.It was not a training to polish our skills, but just to let us know the infrastructure that we are going to manage.

have you signed a surety / service bond in the organisation? if not on what basis they are asking for compensation. can you share the legal notice?

Dear Moses,
I didn't sign any bond in stamp paper, but, as i stated earlier, there was a clause in the offer letter that i signed during the joining, something like "you need to stay here for at least one year".