XBee Pro remote module in API responds to commands but reverts to previous setting on reset

I am sending commands to a remote module in API mode via a coordinator module using API command request 0x17. The remote is in sleep mode 4. The remote responds correctly to commands such as SP command but when I reset the remote module by turning the power off and on the module reverts to the previous setting. For example I change the sleep period from 30 seconds to 5 and the unit immediately starts to send data at the requested 5 second interval. I turn the unit off and on and it reverts to the 30 second interval. What am I doing wrong?