Tell that party of whom gst no wrongly entered.... Reject it in their GSTR2A when windows is opened.... And ur correct gst no party upload it in their GSTR2 as missing invoice in their GSTR2 and u accept it in ur GSTR1A
Sir now no GSTR3 filing has been started... He can take provisional credit in their GSTR3B... And buyer has also the option na in their GSTR2 to add their missing invoices... So why u r worrying.... And before entering GST no of any party check it at GST portal site their GST NO Either by pan no or gst no or tin no.... Be correct at urself