How you join a private telephone group call is all determined by how you're invited to the call by the organiser when setting up the call.
Dialling into the call
If you're dialling into the scheduled call, dial 0300 373 0965 when you're ready. The system will recognise the scheduled call you're invited to, and connect you automatically.
Scheduled for automatic dial out
You don't need to make the call yourself. At the scheduled start time, you'll receive a call from 0300 373 0965.
Scheduled for facilitator dial out
The facilitator will initiate the call. Your phone will ring, and you'll see 0300 373 0965 calling you.