This is meant for call manager 6.x
Sometimes there is a requirement of subscribing a new service(s) to the existing phones in call manager. The steps to do the same are documented below as this issue comes up quite frequently.
Please navigate to Bulk Administration > Phones > Phone Button Template > Add New > Select the Phone Model ( say 7961 ) > Select the required settings on the next page and click save > Now on the same page at the top right corner where it says “Related Links” click on the dropdown and select Subscribe/Unsubscribe services > Subscribe the new service(s) that you have created from here > Save > Save
Then go to Bulk Administration > Phones > Update Phones > Query > Select the phones using Device Type or any other filter and click next > On the next page there is an option “Add all services from this template ”, please check the box against it and select the required template and update
This will activate the new service(s) on the phones once they are reset.