call forwarding ios15 iphone 13 pro max

i am having issues using call forwarding, i seen online *#61# to see what comes up and it states "error performing request unknown error"

"service interrogation failed voice call forwarding when unanswered"

"setting interrogation failed data call forwarding when unanswered "

and the list goes on

just want to learn how to forward and unforwarded calls, even disable them without having to call service provider, also to see if my phone number is forwarded and to which voicemail