Threatening email for not serving 2 months of notice period

I had got offer letter from a company, and post working for 2 days, I had told them that I do not want to work with them any longer. Since then they have been threatening me that if I do not server 2 months notice period I will have to pay them 2 months salary. The clause in the offer letter had this: 'Voluntary termination of employment by the employee shall be made in written two months prior to anticipate termination date. Mailed notices shall be addressed to the employer’s principal place of business, but each party may change the address for notice purposes by written notice to the other in accordance with this paragraph. Violation of this paragraph shall result in loss of compensation and/or appropriate benefits.' I told them I do not want any compensation for the 2 days just let go of me. Now they have threatened they will send me a legal notice. The offer letter never mentions I will have to pay them 2 months of salary incase I do not serve the notice period. Can they take any legal actions based on the above clause?