I want to know the reason i get this banned
If I may... Can you log in and play pvp on your ps4? This is not a notification of a ban/suspension... This is a message related to trying to use cross save and the error is leading to this information on you notification.. this means it could just be an error... if you are not having issues on your console. If you are unable to play pvp on your console and there is a message informing you that you can not play.. then there is something else going on that your account is getting suspended for.
banned? or restricted? what message did you get? if it said 'not so fast', that's a ban and it's permanent and won't be discussed. if it's a restriction, you have internet issues that have caused you to be restricted from entering match making activities (pvp, i.e. crucible, gambit, etc).