Within the claim in Xactimate, click on the "Claim Info" tab on the left hand side. Navigate to the Personnel section and click on the details icon shown below:

The Claim Rep box will appear. Click the "Edit..." button to be taken to the Edit Claim Rep page:

Once you have the Edit Claim Rep page open, add or update your mobile number and/or email address. Ensure the phone type is listed as "Cellular" and that the "Primary" box is checked:

Click "OK" to save your contact information.