can an employee join a competator company

I worked in an company for 2 years and 9 months. I use to have day in and out trouble with my immediate supervisor in my daily work. He basically harassed me with work. The company had an agreement that restricts me from joining to competition for a period of 12 months after resigning from the company. Now, I got a good opportunity from a competition company which is definitely better for my career growth. I have given resignation from my services with a notice period of one month, as per company policy. The GM-HR immediately provided me a letter on the next day for not reporting to duties further after taking away all company belongings for me. The GM - HR threatened me to ruin my career and withheld all my FnF settlement including PF. My new employer HR is insisting for relieving letter from my previous employer which I am unable to produce. My notice period of 2 month ends on 26th April, 2015