This must be done on the line being forwarded. Usually when someone sets up the forwarding to a different number it cancels the first one. You should get a hold of the device and dial *73 to stop all forwarding then do the steps to set forwarding to the next number. Also, talk to your co-workers about their refusal to help with the work load.

The phone that gets forwarded to me is in Illinois, while I am in Iowa, about 3 hours away.  It's not that the co-workers refuse to help, it's that sometimes the next person forgets to turn off the forwarding.  Thank you for your answer though.

While sprmankalel is 100% correct that this must be done on the device/line that  is being forwarded-- another alternative for cancelling or changing the number the call forwarding is set up for is to call in and have a rep do this over the phone.          

I mention this so you know you do have another option aside from relying on your co-worker to cancel the forwarding from that device as this most certainly can be done as well over the phone via a call to  *611/800-922-0204

Do you have access to login to the My Verizon page associated with the phone?  If so, you (all those involved) could remotely set/change the call forwarding when needed.