forgotten passcode

I bought a new iphone X with the larger screen and sold my 1st iphone X to my cousin . He didn't like it so I bought it back . My cousin didn't know how to do a hard reset and just returned it . By the time I noticed that the phone had not reset I called my cousin and he had forgotten the pass code . The locked screen says your iphone has been disabled connect to itunes . So I connected the phone to itunes amd followed the instructions on the help option to update and restore and after say about 15 minutes itunes kicks out and the iphone goes back to the message disabled connect to itunes . I have retried this process 4 or 5 times with the same results .

Please help , Lister16