It seems all your buyers are not aware of Gcash's Crypto features you can ask them to send you USDT or any Crypto that you all both agreed, you don't have to use Gcash or get verified, if all your buyers are not Crypto users they have to first get verified to be able to access the Crypto feature of Gcash.
I just want to add that if the buyer doesn't know about the crypto feature on Gcash and they are not verified accounts, there are step-by-step tutorials on YouTube on how to verify Gcash accounts, how to use the Gcash crypto feature, how to exchange fiat into crypto and send crypto to other addresses.