By mistake wrong gst no. given to suppliers for purchases.

a client was registered in vat, he was issued a provisional id, which he has given to all suppliers for purchases, but instead of migrating, he has taken a new registration number for which he is filing returns regularly, when today we were checking entries in gstr2A we got to know that there is no entry as all suppliers are using that old no. in their gstr 1, please suggest how can client take benefit of itc.