Regisnation declined by employers

In my offer letter there was not mentioned any clauses that I need to sign a commitment letter in time of joining but when I went to the company for joining then after the joining later company force me to sign one commitment letter where it was stated that company will spend money resource and time for me so that I can't leave the company for 3 years. I spend 2 years in the company but company never arrange any training any skill upgradation course for me. From the joining day I took the KT for one implement project and in 10-15 days I started the client handling. Now I got a better offer and submit my regisnation, 1-2 times HR called me and asked for negotiate and one day HR asked me to visit the office to meet her in that time HR was very rough and she verbally informed me that company will not give me the release also she will not going to reply my email. Again mentioning all this I send her one mail and asked for immediate release. But now HR reply back and mentioned that as I signed commitment letter so company will not give me any release.