Tan mismatch

Hi,

My client has got 143(1) intimation which states difference in TDS amount claimed in the return and as per 143(1) computation . Actually his employer sold him company after he left. He received form 16 Part A with TAN no. of previous company and part B with new company's TAN . Form  26 AS is reflecting TDS amount against TAN of previous company. How to get this corrected?

Please guide. Thanks.