You will not be able to change and have the VISA for the new company until you have the NOC from the existing sponsor.

You can choose the option of having a Dubai Visa and profession as Asst Sales Manager and then you can have an on arrival visa in Qatar . which you can extend and stay 3months , everytime. Though to work this way is illegal many are doing this . Also Indians with GCC resident visa do not have any problem in obtaining on arrival visa in Qatar . Tinkerball , please note this...