URLSession background uploadTask is slow on cellular

Question

I am uploading a file using uploadTask created on a single background URLSession. This is working fine on WiFi, but the uploads are really slow on Cellular data. This is how I am creating the URLSession

        var configuration = URLSessionConfiguration.background(withIdentifier: "a unique identifier")
        configuration.isDiscretionary = false
        configuration.allowsCellularAccess = true
        configuration.allowsExpensiveNetworkAccess = true
        configuration.allowsConstrainedNetworkAccess = true
        configuration.networkServiceType = .responsiveData
        let session = URLSession(configuration: configuration, delegate: self, delegateQueue: nil)
        return session
    }()```
Can somebody help me with this please?