Hi Niharika! On the trek, the network which will be available in majority of the places is BSNL, including at the Kedarkantha Peak. Vodafone has also been known to work in some sections. But you should be prepared for having minimum or no network at all, throughout the trek because network availability is highly subjective.
Hey Niharika.. There is barely any network after you cross Purola. You will get BSNL network but it fluctuates sometimes too so be prepared to not have access to good network for 4 days. Make sure you make important calls before crossing Purola.