How to merge a new call to an exciting call in CallKit

Question

I have added CallKit with PushKit which works fine for the first call (Shows just Answer and Decline). I need to merge calls if another user calls while in a call, but I only get End & Accept, Decline and Hold & Accept options. Is it possible to merge calls in the same application?

private var primaryCallUUID: UUID?

func reportIncomingCallFor(handle: String, serial: String, mySerial: String, isVideo: Bool) {
    let uuid = UUID()

    let update = CXCallUpdate()
    update.supportsGrouping = true
    update.remoteHandle = CXHandle(type: .generic, value: handle)
    update.hasVideo = isVideo

    provider.reportNewIncomingCall(with: uuid, update: update) { error in
        if let error = error {
            print("Error: \(error.localizedDescription)")
        } else {
            if self.primaryCallUUID == nil {
                self.primaryCallUUID = uuid // Set the first call as primary
            } else {
                self.mergeCallsIntoGroup(with: uuid)
            }
        }
    }
}

private func mergeCallsIntoGroup(with newCallUUID: UUID) {
    guard let primaryCallUUID = self.primaryCallUUID else { return }

    let mergeCallAction = CXSetGroupCallAction(call: primaryCallUUID, callUUIDToGroupWith: newCallUUID)
    let transaction = CXTransaction(action: mergeCallAction)

    callController.request(transaction) { error in
        if let error = error {
            print("Error merging calls: \(error.localizedDescription)")
        } else {
            print("Successfully merged calls into a group")
        }
    }
}

We simply need to accept the incoming call without holding or ending the existing one, and the app will handle everything else seamlessly.

Any leads on this would be highly appreciated.