What is the difference between your role in the new company and in the previous company ? Are you making changes for monetary gains ? Since you have 3 years work experience, you have some time (2 years) before getting an MBA. You can join the new company work hard for 6 months , then give GMAT in the next 6-8 months and apply with 5 years of experience. Having said that if your new company is only marginally better (the probable case in India
) then you are better off focusing 1 year on GMAT and try to get 750-760. This would help much more than joining a slightly better company.
It's easy to say you can't do it , you are not good enough. It's much harder to step in your shoes and achieve the improbable.