How do I use call divert on my Nokia C1-00?

To set a call divert, select Menu > Settings > Call settings > Call divert and the availalbe options.

To set a call divert only if the SIM card cannot connect to the network, you can also select Goto > Two SIM setting or MenuSettings > Two SIM setting, and then select the desired SIM card and Options > Divert if out of reach.