Can why not. But you cannot direct mnp celcom postpaid to celcom prepaid. Like that cannot.

1) settle all your bill

2) Mnp to others telco first. Digi,maxis,umobile etc etc etc

3) after manage Mnp. Must wait 1-2 weeks. This one depends some said 2-3 days only

3) then Mnp to celcom

Problem solved.