Mar19 GSTR1 details filed in Apr19

Dear Sir/Madam,

I missed Mar19 sales details in GSTR1, so I submited Mar19 sales details in Apr19 GSTR1 with Mar19 dates. But my customer did not get ITC in FY2018-19, My customer GSTR2A of Mar19 is Nil , As finance year close he wants ITC in particular year only. What should i this scenerio? Kindly suggest me , Thanks in advance.

Thank you.