Please be advised that at the time of requesting a new residence permit, you must be officially employed by the new employer for at least three months. If you now simply switch from one employer to another, then your current residence permit will be annuled, since the basis on which you received your current residence permit will no longer exist. Therefore, you need to officially start employment relationship with a new employer as quickly as possible and, as soon as 3 months have passed (but not earlier), you will be able to apply for a new residence permit at once.