Discontinuing SES Subscription on OpenRail

I require information on how to terminate SES on a number of OpenRail licenses.  We have CulvertMaster, FlowMaster, Microstation, and 4 No. OpenRail licenses and want to terminate the subscription on Microstation and 3 No. Openrail licenses.

I cannot find any documentation on how to initiate such a process.  Any assistance will be appreciated.