setup router to endpoint wirelessly

I am using a pc connected to a coordinater. I am using Xbee pro 2sb devices. I also use one Router and up to 20 endpoint sensors. Some of the endpoint sensors were accidentally set up as Routers. I only have wireless connections to these (Routers which should be endpoints). How can I set these Routers to endpoints. I used XCTU but cannot set them to endpoints.

You only have the ability to set as an End device if the node connected to the PC is in API mode and the firmware version installed on your Routers supports the SM command. Your only other option again is to use API mode on the PC node and perform an over the air firmware upgrade. Just understand that with 20 end nodes, you will have to have two always on parent nodes.