Hey Tsepiso, since the Call Forwarding setting is SIM card-based, try in a different SIM card on the Mobicel Metro - then try calling it and observe. If the issue persist, then you know your SIM card is not the issue (otherwise you will have to contact your Carrier/Service Provider). From which finding, you will have to proceed to clearing data - to do this, download and ran the app called "App cache cleaner" from Google play Store. If the issue persist, then you will have to backup your data using the app called Carbon and the proceed to reset your Metro as follows:
>Backup & Restore
>factory data reset
After setting up your phone again, you will install the Carbon app again and then Restore the backup. Let us know if you still need additional help on this.