Swtiching the Company

Question

I am working on C#.net developer  in startup based company which giving 6K pm , now i am  swtiching the company which is also product based , much bigger , well established than current and same language also  which giving higher salary , but this current company requesting not to leave company for atleast 2 months but I Had given joining date also in next company what should I do now ?   to work in same company leave the next company  , or negotitate the request and join the next company