Legal notice from old company for joining new company

I was working for a software company and resigned from there 2 months back. After that I joined the client company of my previous company. I got the legal notice from my previous company for joining client company. My previous company made me sign a contract for not joining any client company for the period of 1 year. I had no other choice other than signing that contract as they would have fired me. That legal notice says I have to resign from the current company, otherwise they will drag me to the court.

I already consulted a lawyer, one of them is telling to resign will be a better option and another lawyer told nothing to worry. You are free to work for anyone no one can stop you . But resigning is very difficult for me at this point of time. Please help me in this situation, as I am not sure what to do next.