As long as have an NOC from the old sponsor you DON'T require to exit from Qatar and it can be transferable within Qatar to your new sponsor.
In case if you want to cancel your existing RP and would like to come in new sponsor visa Qatar immigration system does not allow to cancel your visa until your family memeber's visa cancelled.
If you cancel your family visa you will have to wait another 6 months to apply against once your starts with new sponsor.
Conclusion. Better to change your sponsor without exit and its allowed with NOC
Dear Irsahd,
As long as have an NOC from the old sponsor you DON'T require to exit from Qatar and it can be transferable within Qatar to your new sponsor.
In case if you want to cancel your existing RP and would like to come in new sponsor visa Qatar immigration system does not allow to cancel your visa until your family memeber's visa cancelled.
If you cancel your family visa you will have to wait another 6 months to apply against once your starts with new sponsor.
Conclusion. Better to change your sponsor without exit and its allowed with NOC