You can respond to a conference call invite via the link that is is in the invite SMS or invite email.
After clicking the link, you can then choose whether if you are available for the call.
If you are available for the call, you are then prompted to select a number to be called on. You can either choose to be called on a number that is stored in the Sentinel system or input your own custom number.
Note: After you choose the number you wish to be called on for the given call, you will be unable to change it. So ensure that your phone numbers in the Sentinel system are all up to date and correct if you choose a number.