Like any other traditional banks in Nigeria, you expect OPay to have a Swift Code. Well, OPay does not have a Swift Code because it isn't permit to do. OPay is a licensed mobile money operator (MMO) in Nigeria, not an International Money Transfer (IMT) like Flutterwave.
However, a SWIFT Code in banking is an international bank code that's used by financial institutions to identifies a particular bank worldwide. It's also known as a Bank Identifier Code (BIC).
In Nigeria, only licensed commercial banks have a SWIFT code. Digital banks like OPay, PalmPay, Kudabank or Moniepoint does not have the power to attain a SWIFT Code.
However, for these banks to carryout any international transfer, they must partner with IMT agency like TransferWife, WorldRemit e.t.c., commercial banks like United Bank for Africa (UBA), GTBanks and First Bank of Nigeria (FBN).
In a nutshell, OPay does not possess a SWIFT Code in Nigeria. To get paid from abroad, you need to use any commercial banks in Nigeria. You can simply get such bank Swift Code from their website.