Regarding refund

Sir we are accountants,We want to know that we have filed income tax return for the assessment year 20/21,but most of cases we have not in receipt of income tax refund,whereas the returns have been verified th e-verification and th cpc.From the available sources I found that if the assesee hasnot received the refund,then in cases assessee are eligible to file the revised return.Sir please guide us.Thanks.