You can easily determine if your phone number has been forwarded using some simple USSD codes, such as, *#21#, ##002#, *#62#. You can contact your service provider and get a clear idea about which code to use to detect if your phone number has been forwarded.
In case you want to disable call forwarding from your phone, you can go to ‘Settings’, select the three-dots option, go to ‘Call Forwarding’ or ‘Supplementary Services’ and click to disable.