Sometimes you say like "my employer is not willing to give release" and sometimes like "my sponsor is not giving NOC or release saying that they have given to my Employer". please rephrase your sentence. There is a lot of confusion reading it.

Anyway what i understood is that you came to qatar on a business visit visa and managed to get an RP stamped by your sponsor. Then you got an offer of employment with a bank, in order to start the process of changeover there's a barrier from your sponsor. is this what you are trying to say?.

If your sponsor is not willing to release you for another job, you still have an option of no objection certificate from him which allows you to come back immediately to doha in a couple of days on a new visa. If he doesn't allow you for NOC too then it needs atleast two years to enter in to doha.

However, you can try wheather it is possible to enter doha by business visit visa. Try any office doing PR services and enquire them properly to understand your situation better. Try calling 4443469 and talk to them wheather they can arrange a business visit visa if in case of leaving on cancel.