How do I resolve a mismatch in samaccount and defaultemailaddress of a provisioned user?

I created a new user Stephanie Nwankwankwo whose character count exceeded 20 and was shortened to S.Nwankwanko@domain.com. However, an automatic synchronization process reverted the defaultemailaddress to Stephanie.Nwankwankwo@domain.com while the samaccount remains S.Nwankwanko@domain.com, there is a duplicate email address in Entra ID reflecting both email addresses. How can I resolve it?