not possible if you already posted a receipt. Having posted a receipt would also mean that you posted the GR value based on the PO price, so what do you expect from changing an indicator that late in the process? Reversing all amounts and replacing them with zero, adjusting moving average prices even in case further movements had already happened? No. that is not how SAP works, if you have already follow on documents then you have to cancel those first before you can change an indicator.

see OSS note 587759 - ME22N: goods receipt/invoice receipt control indicator

it says : After the posting of follow-on documents you should no longer change the indicators for the expected goods receipt and for goods receipt-related invoice verification, unless the effects of the documents were undone!